Academic literature on the topic 'Fluid flow theory in petroleum drilling'

During horizontal directional drilling (HDD), the drilling fluid pressure must not surpass the maximum allowable pressure to minimize the risk of hydraulic fracturing; hence, a plan pressure can be used to manage the drilling fluid pressure. This paper addresses the prediction of plan annular pressure using the power law flow model. The annular pressures were predicted using the power law model with rheological parameters determined from a six-speed viscometer with varying shear rate ranges from 3 to 600 RPM for two HDD projects, and the predicted pressures were compared with the measurements. The results indicated that the annular pressure could be properly predicted, and the best prediction was achieved by the shear rate range of 6–100 RPM due to embracing the real shear rate of drilling fluid inside the annulus; this shear rate range is close to the recommendation (3–100 RPM) by American Petroleum Institute Recommended Practice.

In this Special Issue, all aspects of fluid flow and heat transfer in geothermal applications, including the ground heat exchanger, conduction, and convection in porous media, are considered. The emphasis here is on mathematical and computational aspects of fluid flow in conventional and unconventional reservoirs, geothermal engineering, fluid flow and heat transfer in drilling engineering, and enhanced oil recovery (hydraulic fracturing, steam-assisted gravity drainage (SAGD), CO2 injection, etc.) applications.

Wellbore instability, experienced mainly in shale sections, has resulted in significant drilling delays and suspension of wells in major Australian petroleum basins. These instabilities may be induced by either in-situ stresses that are high relative to the strength of the formations or physico-chemical interactions of the drilling fluid with the shales.This paper describes fundamental concepts of mud pressure penetration and flow of water between the wellbore and formation due to their chemical potential difference, and associated mud support changes as the drilling fluid interacts with shales. Due to the low permeability of shales, the penetration of the drilling fluid filtrate would result in an increase in pore pressure over a considerable distance from the wellbore. This instability mechanism strongly depends on properties of the drilling fluid filtrate and pore fluid, and the rock material composition.In addition to mud pressure penetration, water would be induced to either flow into or out of the formation depending on the relative chemical potential of the drilling fluid and the formation. A more stable wellbore condition could be achieved by optimising the chemical potential of drilling fluids.Drilling fluid and shale properties required for the models, which are determined using analytical and laboratory techniques, are presented herein. The effects of the time-dependent mechanisms on wellbore stability are demonstrated for a polyacrylamide, an ester-based and an oil-based mud. The results demonstrate that a more effective mud support can be obtained by optimising the adhesion and viscosity of the drilling fluid filtrate, and chemical potential of the drilling fluid.

Summary This paper presents a discussion of the issues related to the interaction between rock deformation and multiphase fluid flow behavior in hydrocarbon reservoirs. Pore-pressure and temperature changes resulting from production and fluid injection can induce rock deformations, which should be accounted for in reservoir modeling. Deformation can affect the permeability and pore compressibility of the reservoir rock. In turn, the pore pressures will vary owing to changes in the pore volume. This paper presents the formulation of Biot's equations for multiphase fluid flow in deformable porous media. Based on this formulation, it is argued that rock deformation and multiphase fluid flow are fully coupled processes that should be accounted for simultaneously, and can only be decoupled for predefined simple loading conditions. In general, it is shown that reservoir simulators neglect or simplify important geomechanical aspects that can impact reservoir productivity. This is attributed to the fact that the only rock mechanical parameter involved in reservoir simulations is pore compressibility. This parameter is shown to be insufficient in representing aspects of rock behavior such as stress-path dependency and dilatancy, which require a full tensorial constitutive relation. Furthermore, the pore-pressure changes caused by the applied loads from nonpay rock and the influence of nonpay rock on reservoir deformability cannot be accounted for simply by adjusting the pore compressibility. Introduction In the last two decades, there has been a strong emphasis on the importance of geomechanics in several petroleum engineering activities such as drilling, borehole stability, hydraulic fracturing, and production-induced compaction and subsidence. In these areas, in-situ stresses and rock deformations, in addition to fluid-flow behavior, are key parameters. The interaction between geomechanics and multiphase fluid flow is widely recognized in hydraulic fracturing. For instance, Advani et al.1 and Settari et al.2 have shown the importance of fracture-induced in-situ stress changes and deformations on reservoir behavior and how hydraulic fracturing can be coupled with reservoir simulators. However, in other applications, geomechanics, if not entirely neglected, is still treated as a separate aspect from multiphase fluid flow. By treating the two fields as separate issues, the tendency for each field is to simplify and make approximate assumptions for the other field. This is expected because of the complexity of treating geomechanics and multiphase fluid flow as coupled processes. Recently, there has been a growing interest in the importance of geomechanics in reservoir simulation, particularly in the case of heavy oil or bituminous sand reservoirs,3,4 water injection in fractured and heterogeneous reservoirs,5–7 and compacting and subsiding fields.8,9 Several approaches have been proposed to implement geomechanical effects into reservoir simulation. The approaches differ on the elements of geomechanics that should be implemented and the degree to which these elements are coupled to multiphase fluid flow. The objective of this paper is to illustrate the importance of geomechanics on multiphase flow behavior in hydrocarbon reservoirs. An extension of Biot's theory10 for 3D consolidation in porous media to multiphase fluids, which was proposed by Lewis and Sukirman,11 will be reviewed and used to clarify the issues involved in coupling fluid flow and rock deformation in reservoir simulators. It will be shown that for reservoirs with relatively deformable rock, fluid flow and reservoir deformation are fully coupled processes, and that such coupled behaviors cannot be represented sufficiently by a pore-compressibility parameter alone, as is done in reservoir simulators. The finite-element implementation of the fully coupled equations and the application of the finite-element models to an example problem are presented to illustrate the importance of coupling rock deformation and fluid flow. Multiphase Fluid Flow in Deformable Porous Media Fig. 1 illustrates the main parameters involved in the flow of multiphase fluids in deformable porous media and how these parameters ideally interact. The main quantities required to predict fluid movement and productivity in a reservoir are the fluid pressures (and temperatures, in case of nonisothermal problems). Fluid pressures also partly carry the loads, which are transmitted by the surrounding rock (particularly the overburden) to the reservoir. A change in fluid pressure will change the effective stresses following Terzaghi's12 effective stress principle and cause the reservoir rock to deform (additional deformations are induced by temperature changes in nonisothermal problems). These interactions suggest two types of fluid flow and rock deformation coupling:Stress-permeability coupling, where the changes in pore structure caused by rock deformation affect permeability and fluid flow.Deformation-fluid pressure coupling, where the rock deformation affects fluid pressure and vice versa. The nature of these couplings, specifically the second type, are discussed in detail in the next section. Stress-Permeability Coupling This type of coupling is one where stress changes modify the pore structure and the permeability of the reservoir rock. A common approach is to assume that the permeability is dependent on porosity, as in the Carman-Kozeny relation commonly used in basin simulators. Because porosity is dependent on effective stresses, permeability is effectively stress-dependent. Another important effect, in addition to the change in the magnitude of permeability, is on the change in directionality of fluid flow. This is the case for rocks with anisotropic permeabilities, where the full permeability tensor can be modified by the deformation of the rock. Examples of stress-dependent reservoir modeling are given by Koutsabeloulis et al.6 and Gutierrez and Makurat.7 In both examples, the main aim of the coupling is to account for the effects of in-situ stress changes on fractured reservoir rock permeability, which in turn affect the fluid pressures and the stress field. The motivation for the model comes from the field studies done by Heffer et al.5 showing that there is a strong correlation between the orientation of the principal in-situ stresses with the directionality of flow in fractured reservoirs during water injection. There is also growing evidence that the earth's crust is generally in a metastable state, where most faults and fractures are critically stressed and are on the verge of further slip.13 This situation will broaden the range of cases with strong potential for coupling of fluid flow and deformation.

The generalized hyperbolic non-Newtonian fluid model first proposed by Al-Zahrani [J. Petroleum Sci. Eng. 17, 211 (1997)] is considered. This model was successfully applied to some drilling fluids with a better performance in relating shear stress and velocity gradient compared to power-law and the Hershel-Bulkley model. Special flow geometries namely pipe flow, parallel plate flow, and flow between two rotating cylinders are treated. For the first two cases, analytical solutions of velocity profiles and discharges in the form of integrals are presented. These quantities are calculated by numerically evaluating the integrals. For the flow between two rotating cylinders, the differential equation is solved by the Runge-Kutta method combined with shooting. For all problems, the power-law approximation of the model is compared with the generalized hyperbolic model, too.

In order to understand how a particulate plug may evolve within the flow of an essentially homogeneous suspension, we have developed a fluid-particle flow model. This theoretical model is based upon a monodisperse collection of rigid, spherical particles suspended in an incompressible, Newtonian liquid. Balance equations of mass and momentum are given for each phase within the context of a continuum mixture theory. The interactions between the phases are dominated by interfacial drag forces and unequilibrated pressure forces. The pressure associated with the solid particles is given by a phenomenological model based upon the flow dynamics. Of primary concern is the calculation of solid particle concentrations within a flow field to indicate the initiation of a particulate plug.

Summary This paper proposes a method for quantitative integration of seismic(elastic) anisotropy attributes with reservoir-performance data as an aid in characterizing systems of natural fractures in hydrocarbon reservoirs. This method is demonstrated through application to history matching of reservoir performance using synthetic test cases. Discrete-feature-network (DFN) modeling is a powerful tool for developing fieldwide stochastic realizations of fracture networks in petroleum reservoirs. Such models are typically well conditioned in the vicinity of the wellbore through incorporation of core data, borehole imagery, and pressure-transient data. Model uncertainty generally increases with distance from the borehole. Three-dimensional seismic data provide uncalibrated information throughout the interwell space. Some elementary seismic attributes such as horizon curvature and impedance anomalies have been used to guide estimates of fracture trend and intensity (fracture area per unit volume) in DFN modeling through geostatistical calibration with borehole and other data. However, these attributes often provide only weak statistical correlation with fracture-system characteristics. The presence of a system of natural fractures in a reservoir induces elastic anisotropy that can be observed in seismic data. Elastic attributes such as azimuthally dependent normal move out velocity (ANMO), reflection amplitude vs. azimuth (AVAZ), and shear-wave birefringence can be inverted from 3D-seismicdata. Anisotropic elastic theory provides physical relationships among these attributes and fracture-system properties such as trend and intensity. Effective-elastic-media models allow forward modeling of elastic properties for fractured media. A technique has been developed in which both reservoir-performance data and seismic anisotropic attributes are used in an objective function for gradient-based optimization of selected fracture-system parameters. The proposed integration method involves parallel workflows for effective elastic and effective permeability media modeling from an initial DFN estimate of the fracture system. The objective function is minimized through systematic updates of selected fracture-population parameters. Synthetic data cases show that3D-seismic attributes contribute significantly to the reduction of ambiguity in estimates of fracture-system characteristics in the interwell rock mass. The method will benefit enhanced-oil-recovery (EOR) program planning and management, optimization of horizontal-well trajectory and completion design, and borehole-stability studies. Introduction Anisotropy and heterogeneity in reservoir permeability present challenges during the development of hydrocarbon reserves in naturally fractured reservoirs. Predicting primary reservoir performance, planning development drilling or EOR programs, completion design, and facilities design all require accurate estimates of reservoir properties and the predictions of future reservoir behavior computed from such estimates. Over the history of naturally-fractured-reservoir development, many methods have been used to characterize fracture systems and their effect on fluid flow in the reservoir. These include the use of geologic surface-outcrop analogs; core, single-well, and multiwell pressure-transient analysis; borehole-imaging logs; and surface and borehole seismic observations. To date, efforts to integrate seismic data into the workflow for characterization of naturally fractured reservoirs have been focused on the use of post-stack data. CDP stacking of seismic data takes advantage of redundancy in seismic data sets for the attenuation of noise. Unfortunately, CDP stacking also eliminates valuable information about spatial and orientational variations in the data. Such variations are often related to fracture-system characteristics. CDP-stacked seismic data are typically used to define the main structural elements of the reservoir. Fracture density has been correlated successfully with horizon curvature determined from seismic horizons. Seismic attributes frequently can be correlated with reservoir properties such as shale fraction, which often correlates with fracture-population statistics. Acoustic impedance computed from seismic data frequently exhibits dim spots in the presence of fractures.

Particle Impact Drilling technology (PID) is a new drilling technology, which is designed especially to solve the oil and gas exploration under hard terrane. In PID system, the steel particles were added in the drilling fluid to impact rock. The particles would be recycled and put to use again, thus it is of great significance to adjust proper drilling fluid flow rate for steel particle’s reflux. The flow rate of drilling fluids carrying particles is influenced by the fluid viscosity, the annular gap between drill pipe and wellbore, the particle volume fraction and particle size, etc. This paper mainly studied the influence of the annular gap and the flow rate, while the other factors keep constant. Both experimental method and dimension theory were employed in the research. Furthermore, empirical formula was proposed to describe the mechanism.

During drilling of petroleum or geothermal wells, unforeseen circumstances occasionally happen that require suspension of the operation. When the drilling fluid is left in a static condition, solid material like barite may settle out of the fluid. Consequently, the induced hydrostatic pressure that the fluid exerts onto the formation will be reduced, possibly leading to collapse of the borehole or influx of liquid or gas. A possible mitigation action is placement of a gel pill. This gel pill should preferably be able to let settled barite rest on top of it and still transmit the hydrostatic pressure to the well bottom. A bentonite-based gel pill is developed, preventing flow of higher density drilling fluid placed above it to bypass the gel pill. Its rheological behavior was characterized prior to functional testing. The designed gel pill develops sufficient gel structure to accommodate the settled barite. The performance of the gel was tested at vertical and 40° inclination from vertical. Both conventional settling and the Boycott effect were observed. The gel pill provided its intended functionality while barite was settling out of the drilling fluid on top of this gel pill. The barite was then resting on top of the gel pill. It is demonstrated that a purely viscous pill should not be used for separating a high density fluid from a lighter fluid underneath. However, a bentonite or laponite gel pill can be placed into a well for temporary prevention of such intermixing.

Sequel to the environmental problems of the none biodegradable nature of the conventional oil-based drilling fluids, it is imperative and urgent for environmental sustainability and for the development of eco-friendly products, that use of petroleum diesel oil as the continuous phase of drilling mud warrant urgent reconsideration. Towards the search to provide a better alternative to petroleum diesel oil as a base oil for drilling mud, vegetable oil from the inedible seeds of the African star apple fruits, was examined In this study, an oil-based drilling mud (OBM) with biodegradable qualities for sustainable environmental applications was developed and characterized. The OBM was produced with chrysophyllum albidum (African star apple) oil methyl ester bio-lubricant to replace petroleum diesel as the continuous phase of the mud. The chrysophyllum albidum oil methyl ester was synthesized from fatty acid methyl ester obtained through transesterification process of none edible oils extracted from chrysophyllum albidum seeds. Tests of physiochemical and rheological properties were carried out on mud samples of chrysophyllum albidum oil biolube-based mud (CAOBBM) and petroleum diesel oil-based mud (PDOBM) to characterise the fluids for performance evaluation and environmental consequences. The findings indicated that CAOBBM was lower in density and less acidic than PDOBM, at barite content of 20 g. Also, CAOBBM had lower viscosity which implies less resistance to flow and lower pressure losses. The low oil to water ratio from the filtration loss test, revealed that CAOBBM is more viable to low fluid loss and consequently enhances wellbore stability and less oil retained on drilled cuttings. Similarly, toxicity test confirmed CAOBBM to be more appropriate and less detrimental to the environment compared to PDOBM. Summarily chrysophyllum albidum oil biolube based muds stands safer and more eco-friendly for a sustainable environment than petroleum diesel oil-based muds.

This thesis presents the results of the investigations in two areas, i.e. non-Newtonian annular flow and cuttings transport in drilling annuli at various angles. In the first part of the thesis, a review of the fundamentals and the previous studies on laminar concentric annular flow of non-Newtonian fluids is given at first. Then two parallel theoretical studies are performed, respectively, on: a. Laminar eccentric annular flow of power-law and Bingham plastic fluids. In this analysis, a new method is used which treats an eccentric annulus as infinite number of concentric annuli with variable outer radius. The analytical solutions of the shear stress, shear rate, velocity and the volumetric flowrate/pressure gradient are obtained over the entire eccentric annulus. This analysis is useful in design of any engineering operations related to eccentric annular flow such as oil drilling operations. b. Laminar helical flow of power-law fluids through concentric annuli. A group of dimensionless equations are derived in this analysis for the profiles of the apparent viscosity, angular and .axial velocities, and for the volumetric flowrate. These equations are essential when one needs to simulate the helical flow conditions in various engineering operations. In addition, another group of dimensionless equations are also derived for pressure gradient calculations which can be used directly by drilling engineers to predict the reduction of the annular friction pressure drop caused by drillpipe rotation during drilling operations. The second part of the thesis is dedicated to the investigations into the problems directly related to cuttings transport through drilling annuli at various angles. First, both theoretical and experimental studies on settling velocities of drilled cuttings in drilling fluids are conducted using new approaches to account for the non-Newtonian nature of drilling fluids and for the shape irregularity of drilled cuttings. Based on experimental results, a generalised model is developed for calculating settling velocities of variously shaped particles in power-law fluids. Then, the effects of various parameters on cuttings transport during drilling operations are analysed based on the previous and the present studies. After that, an extensive theoretical analysis for the previous studies on the minimum transport velocity (MTV) in solid-liquid mixture flow through pipelines, on initiation of sediment transport in open channels and on MTV for cuttings transport in deviated wells is presented. At last, theoretical studies on the minimum transport velocity for cuttings transport in drilling annuli at various angles are conducted and two parallel general correlations are developed. When these correlations are experimentally verified and numerically established in the future, they can be served as general criteria for evaluating and correlating the effects of various parameters on cuttings transport, and as a guideline for cuttings transport programme design during directional drilling.

Abstract Extended reach well (ERW) can be extremely drilled to distant reservoirs to reduce the infrastructure and operational footprint. Drilling ERW and extending their reach to greater depths requires both improved equivalent circulating density (ECD) and frictional resistance due to large horizontal displacement, long open hole and borehole unstability. ECD is one of the keys to safe and efficient drilling, especially in complex formations with narrow pressure profile, and wellbore frictional resistance appreciably influences drilling torque and drag, as well as casing running. This paper presents several methods, including continuous circulating valve(CCV) drilling technology, cuttings bed removal technology and chemical friction reduction technology, to promote the success of ERW drilling. The applications are realized by means of adding CCV, cuttings bed cleaner to the drill string and chemical friction reducer into the drilling fluid. Respectively the CCV drilling technology realizes the continuous circulation of drilling flooding, and cuttings bed removal technique utilize integrated design of hydraulic machinery with hydraulic parameter adjustment and flow passage design, to enhance turbulence velocity and strength of drilling fluid flow field, which both can effectively improve the efficiency of carrying bit cuttings, and reduce the fluctuation of ECD. Chemical friction reduction technology is mainly composed of chemical frictional drag reduction agent which belongs to organic anion compound products, and has excellent super anti-wear lubrication. Results show that the fluctuation of ECD in the high-risk well section with well loss was controlled within 2.5%, and narrow density window formation (0.18g/cm3) was drilled safely without any caving and leakage. The friction coefficient ranged from 0.4 to 0.25, with 40% decrease compared with previous wells in Huizhou Oilfield. And also the ROP increased by 45% due to effective transmission of WOB. The technologies shown in this paper comprise key innovative technologies in ERW operation in Nanhai East. Less time is occupied in equipment installation, as well as simple operation flow, however with improved stability and remarkable performance. It lays a foundation for further study of ultra extended reach wells with greater difficulty and challenge.

Abstract Effective mudcake removal is essential to restore the optimal well productivity/injectivity after different drilling operations. Typically, this objective is achieved by using harsh chemical treatments such as hydrochloric acid (HCl), organic acids and oxidizers. However, these methods have been limited due to associated high corrosion rates, high operation cost, and un-even mudcake removal. This task becomes even more difficult and very challenging in horizontal/multilateral wells. Organic acids and acid precursors have been also used to clean long horizontal wells following drilling operations. However, in long multilateral horizontal wells, fluid placement is considered one of the main challenges with chemical mudcake removal treatments due to accessibility to each lateral and reaching its TD. Additionally, the use of these treatments has poor health, safety and environmental (HSE) footprints. This work provides a workflow and illustrates the use of an in-house designed zero-flaring flowback system to clean up recently drilled multilateral horizontal wells with water-based mud. The system consists of two upstream solid management systems, namely de-sander (cyclone), and sand catcher (filter). Downstream, the choke manifold, 4-phase separator, a downstream solid management equipment, and 3-phase separator are also included. Additionally, there is also a surge tank, as a backup flowback vessel to be used if needed to revive the well and offload any heavy fluids. This tank is used to initially help the well to gain the pressure momentum to naturally flow and offload heavy fluid present in production tubular. The cleanup campaign was successfully and safely completed for effective cleanup of more than 30 openhole horizontal multilateral wells without the use of any chemical treatments. The duration of cleanup operations was optimized using several techniques to effectively and efficiently remove existing mudcake. This paper provides the operational criteria to achieve effective and adequate mudcake removal for horizontal/multilateral wells and restore its optimal performance. Different design parameters and tailored flowback programs will be discussed, which led to effective drawdown pressure to reach optimized natural cleanup of each well. The well simulated flow model was also considered and used as input to design each well specific flowback program and minimize the risks of erosion, solids settlement in pipeline and downstream facilities. As a result, each well cleanup duration was reduced to an average of 1-2 day, while achieving the maximum potential production rate of each treated well.

Wellbore instability was and is one of the most frequent problems in petroleum industry, especially in the drilling operations. It is mainly caused by the shale formations which represent 75% of all drilled formations. The wellbore instability problems involve tight hole spots, wellbore diameter enlargement, the appearance of cavings, the inability of carrying out wireline operations, poor hole cleaning, unsuccessful wellbore cementing operations and other. The wellbore instability is the result of mechanical and physico-chemical causes mostly acting concurrently. The shale instability basically comes out of its mineralogical composition (especially clay minerals content) and physico-chemical properties. Shale-mud interaction includes water/ions movement in and out of the shales due to pressure differential, osmosis, diffusive flow and capillary pressure. Many research activities about shale instability causes and shale properties (affecting shale behavior) definition have been carried out by now. Different shale samples, laboratory equipment and inhibitive muds have been used. Laboratory tested shale samples are provided by the wellbore cores, surface sampling or, which is the simplest method, by collecting the samples at the shale shakers during drilling operation. The amount of these samples is not enough for laboratory testing. Another problem is closely connected to sample quality and preservation. There are also differences in drilling fluids used in these laboratory tests, especially in their composition (sometimes containing more than one shale inhibitor). It is difficult to compare test results and conclusions made by different authors. The laboratory study presented within this paper are done with artificial clay samples (pellets) made by compacting the powderish material containing exact quantity of quartz, montmorillonite and kaolinite. The laboratory testing is done by treating the powderish samples inside the desiccator (24 hours), compacting (30 minutes), swelling (24 hours) and drying samples (24-hour). Sample swelling is tested by using different mud types and the sample mass is measured in each above mentioned phase. Special attention is directed to preparation and pellets content definition as a good replacement for the original shale in laboratory testing of shale and drilling fluid interaction. The influence of used muds on the total pellet swelling and swelling intensity, especially at the early phase of testing was determined.

Abstract The horizontal section length of shale gas horizontal wells in Sichuan Basin in the south-west of China generally exceeds 2000m. Cuttings are apt to accumulate and form cuttings beds along such long and curve horizontal sections due to low cuttings carrying capacity, which often results in excessive torque and drag or even stuck pipes during drilling process. According to the statistics dada inthe period of Jan. - Oct. 2019, more than 25 stuck pipe incidents and 15 rotary steering tools loss in borehole were reported due to inefficient cuttings transportation in the long horizontal wells in Sichuan Basin. This paper studies the cuttings transportation and cuttings bed formation in horizontal wells. A prediction model for the distribution of cuttings bed was established. A monitoring and analysis software for the cuttings bed and cuttings cleaner with V-shaped spiral blades that is used to agitate the cuttings bed wasdeveloped. The software calculates the distribution and thickness of the cuttings bed according to the well trajectory, wellbore structure, drilling fluid characteristics, etc., and provides the optimal operating parameters for the removal of the cuttings bed by the rotating and reciprocating drill string. Then, the drill cuttings remover in the drill string moves to the predicted position of the drill cuttings, scrapes the drill cuttings and creates a swirling flow during the pipe rotation. The combined application of software and makeup remover can effectively solve the issue of borehole cleaning in long horizontal wells. One of the field applications was carried out in the well Ning 209H12, a shale gas horizontal well in Sichuan Basin. The well experienced excessive torque and drag issue during the tripping of drill string of long horizontal section. Thesoftware ran based on oil well data, and it determines the placement and thickness of cuttings beds in the well and calculates the optimal operating parameters for a flow rate of about 32L/s and a speed of 100rpm to remove them. By rotatingand reciprocating the drill string with recommended operating parameters along the cuttings bed interval, the removers helped cleaning the cuttings bed efficiently and significant amount of cuttings was observed at vibration screen. After cleaning the cuttings bed interval, the trip smoothly ran to the bottom without any excessive torque and drag, and then continues to drill in cooperation with the removers to the total depth. During the well completion, there was no problem with the operation of electrical logging and production casing. This cuttings removal technology has been used in other shale gas formations and tight gas formations where horizontal wells are widely used.

Abstract Offshore drilling projects can be as complex as they are costly, and many problems can arise during the drilling and extraction of sub-sea pipelines petroleum, including environmental issues. The oil and gas industry relies on multi-phase, multi-component flow techniques to transport substances such as gas, oil and water through horizontal and sub-sea pipelines. Artic and offshore drill sites can be particularly challenging due to hydrate formation in the transport horizontal and sub-sea pipelines. This study investigates the feasibility of using a four-phase, four-fluid flow Multi-Component through horizontal pipelines to move a four-phase multi-component flow (oil, gas, water, and sand particles) through submerged pipelines. In order to accurately gauge the multi-component mixtures’ hydro- and thermo-dynamic properties, fluid equilibrium and phase-behavior models are constructed. As well, to examine various interrelated factors such as momentum, mass and heat transfer occurring between pipelines walls and flow, a series of equations are developed. In the present study, the effect of temperature and pressure on multi-phase flows in horizontal and sub-sea pipelines is investigated. As well, models of flow patterns and pressure drops are created specifically for horizontal and sub-sea pipeline environments. Note that the terms “Four-Phase and Multi-Component flow” are used interchangeably in this study. And Create pressure drops and flow behavior models of multi-phase flows for horizontal and sub-sea pipelines. Furthermore, multi-phase flows may occur in any one of the following combinations: liquid-gas, liquid-gas-solid, liquid-liquid-gas-solid, An example of a, liquid-liquid-gas-solid flow is four immiscible fluids and component (e.g., water, oil, gas, and solid), immiscible liquids being those which do not form a homogeneous mixture when added together. In terms of practical applications of multi-phase and multi-component flows, water injected into an oil pipelines helps to decreases both the pressure gradient and flow resistance.

Abstract This paper describes a methodology for delineating tar surface, incorporating it into a geological model, and the process for numerical modeling of oil viscosity variation with depth above the tar surface. The methodology integrates well log data and compositional fluid analysis to develop a mathematical model that mimics the oil's property variation with depth. While there are a good number of reservoirs that fit this description globally, there is a knowledge gap in literature regarding best practices for dealing with the peculiar challenges of such reservoirs. These challenges include; (i) how to delineate the top-of-tar across the field, (ii) modeling of Saturation Height Function (SHF) in a system where density and wettability is changing with depth, and (iii) the methodology for representing the depth-dependent oil properties (especially viscosity) in reservoir simulation. Nuclear magnetic resonance (NMR) logs were used to predict fluid viscosity using a technique discussed by Hursan et al. (2016). Viscosity regions are identified at every well that has an NMR log, and these regions are mapped from well to well across the reservoir. Within each viscosity region, the analysis results of fluid samples collected from wells are used to develop mathematical models of fluid composition variation with depth. A reliable SHF model was achieved by incorporating depth-varying oil density and depth varying wettability into the calculation of J-Function. A compositional reservoir simulation was set-up, using the viscosity regions and the mathematical models describing composition variation with depth, for the respective regions. Using information obtained from literature as a starting point, residual oil saturation was modeled as a function of oil viscosity. Original reservoir understanding places the top of non-movable oil (tar) at a constant fieldwide subsurface depth, which corresponds to the shallowest historical no-flow drillstem test (DST) depth. Mapping of the NMR viscosity regions across the field resulted in a sloping tar-oil contact (TOC), which resulted in an increase of movable hydrocarbon pore volume. The viscosity versus depth profile from the simulation model matched the observed data, and allow the simulation model better predict well performance. In addition, the simulation model results also matched the depth-variation of observed formation volume factor (FVF) and reservoir fluid density. Some wells that have measured viscosity data but no NMR logs were used as blind-test wells. The simulation model results also matched the measured viscosity at those blind-test wells. These good matches of the oil property variation with depth gave confidence, that the simulation model could be used as an efficient planning tool for ensuring that injectors are placed just-above the tar mat. The use of the simulation model for well planning could reduce the need for geosteering while drilling flank wells, leading to savings in financial costs. This paper contains a generalized approach that can be used in static and dynamic modeling of reservoirs, where oil changes from light to medium to heavy oil, underlain by tar. It contains recommendations and guidelines to construct a reliable simulation model of such systems.

Polymer fluids are utilized extensively in the petroleum industry for viscosity enhancement and friction pressure reduction during turbulent flow. Selection of the appropriate correlation for the desired fluid and flow regime is very important for the accurate determination of frictional pressure losses. A range of correlations has been published for predicting frictional losses under annular flow conditions. All these correlations are based on certain assumptions, which limit their application under different operating conditions. This paper presents the results of an experimental study carried out to develop a reliable frictional pressure loss correlation for polymeric solutions in a fully eccentric annulus. Fluids investigated include Water, Guar, Xanthan, and Welan gum under conditions typically encountered in drilling and completion operations. The frictional pressure losses of these polymeric fluids exhibiting drag-reducing characteristics are investigated and analyzed as a function of generalized Reynolds number for each fluid. The experimental set-up includes 200 ft of 1 1/2-in. straight tubing, and 200 ft of (3 1/2-in. × 1 3/4-in.) fully eccentric annuli. Data analysis enabled the development of an improved correlation for polymer solutions in a fully eccentric annulus. Fluids apparent viscosity at 511 sec−1, generalized Reynolds number, and diameter ratio, all of which can be easily determined in the field, were selected as independent variables for the new correlation. Experimental data show that the new correlation estimates friction pressure losses in fully eccentric annuli much better than previously published equations.