bluuebunny/crossref_metadata_2025 huggingface dataset:
Solid Particle Deposition During Turbulent Flow Production Operations
Authors: Escobedo Joel , Mansoori G. A.
Published: December 2007

The production and transportation of petroleum fluids could be severely affected by deposition of suspended particles (i.e. asphaltene, paraffin/wax, sand, and/or diamondoid) in the production wells and/or transfer pipelines. In many instances the amount of precipitation is rather large causing complete plugging of these conduits. Therefore, it is important to understand the behavior of suspended particles during flow conditions.

In this paper we present an analysis of the diffusional effects on the rate of solid particle deposition during turbulent flow conditions (crude oil production generally falls within this regime). The turbulent boundary layer theory and the concepts of mass transfer have been utilized to calculate the particle deposition rates on the walls of the flowing conduit. The developed model accounts for the eddy and Brownian diffusivities as well as for inertial effects.

The analysis presented in this paper shows that rates of solid-particle deposition (during crude oil production) on the walls of the flowing channel due solely to diffusional effects are small.

It is also shown that deposition rates decrease with increasing particle size. However, when the process is momentum controlled (large particle sizes) higher deposition rates are expected.
Slack-off Load Transmission in Horizontal and Inclined Wells
Authors: Wu Jiang
Published: December 2007

This paper studies the wall contact force, frictional drag, and slackoff load transmission for tubulars in inclined and horizontal wellbores. The wall contact force of helically buckled tubulars in horizontal and inclined wellbores shows to have the same expression as that in vertical wells. New wall contact force of sinusoidally buckled tubulars is modeled and expressed as half of that of helically buckled tubulars. Equations for the axial load distribution of buckled tubular and the transmitted tubular bottom load are also presented. It is shown that less load is transmitted to the tubular bottom, and helical buckling (or even "lockup") occurs much earlier, when the frictional drag from sinusoidal buckling is considered. The results can be used to improve the frictional drag and load transmission calculation for tubular operations (drillstring, tubing, and coiled tubing) in horizontal and inclined wells.
Statistical Analyses of Shape Factor and Productivity Index for Horizontal Wells
Authors: Faruqi S. A. , Malekzadeh D. , Day J. J.
Published: December 2007

The performance of horizontal wells in bounded anisotropic reservoirs has been investigated using the statistical analysis. New statistical models for calculating the fraction of horizontal well length contributing to unrestricted production, and horizontal well shape factor, are presented.

The concept that the performance of horizontal well of halflength Xfl with mechanical skin can be replaced by the performance of an equivalent horizontal well of half-length Xf2 with no mechanical skin is used. The statistical analysis showed that for a given reservoir shape and well asymmetry, the horizontal well shape factor can be directly correlated with three dimensionless parameters, XLD, rw/h, and LD, which are functions of reservoir and well parameters. These statistical correlations can easily be used to predict the performance of a damaged and/or stimulated horizontal well without the need to use complex numerical and/or analytical solutions which require extensive computer use.
Fracturing Fluid Interactions With Formation Minerals and Their Subsequent Effect on Formation Permeability
Authors: Thompson J. E. , DeVine C. S.
Published: December 2007

The selection process of hydraulic fracturing fluids for oil and gas well stimulation applications largely ignores interactions of the stimulation filtrate and the broken stimulation fluid with formation minerals. Fluid interactions with formation minerals may have a significant influence on formation permeability and subsequent well production. Laboratory formation core regain permeability studies, subsequent to the injection of both low and high pH fluids, were conducted to measure fluid effect on core permeability. Results of these tests indicate that both the rock mineralogy and the pore system morphology are affected by contact of the rock with filtrate from the injection of an unbroken stimulation system into the formation. Formation permeability after treatment with stimulation fluid can be significantly influenced by formation-injection fluid interactions. Studies have demonstrated that, depending on the specific formation mineralogy, post-injection permeability may be increased by low pH systems only, by high pH systems only, or by either low or high pH systems.

The focus of this paper is to identify specific formation minerals which may potentially be affected by contact with fracturing fluid filtrate and broken fracturing fluid and to relate increases in formation permeability to resultant fluid-rock interactions. Mechanisms of fluid-formation interactions and chemical reactions are presented.
Design Guidelines for Artificial Barrier Placement and Their Impact on Fracture Geometry
Authors: Barree Robert D. , Mukherjee Hemanta
Published: December 2007

Fracture height growth can be contained by selective placement of a low mobility bed of proppant along the upper and the lower tips of a propagating hydraulic fracture, while keeping the front tip open to further lateral extension. This is done in a separate treatment step prior to the main treatment. The success of these treatments in reducing height growth depends on the proper design and execution of the treatments, based on knowledge of the vertical stress profile, which dominates the fracture geometry evolution in three dimensional space. Such barrier placements are limited by the rate of early fracture height growth with respect to extension, treatment rate, fluid viscosity, proppant concentration, proppant size and specific gravity. This paper shows the effects of these variables on the effectiveness of the placement of artificial barriers. The paper also describes the three dimensional fracture geometry evolution beyond the lateral extent of the emplaced barriers. Beyond these barriers the fracture loses any artificial containment, and grows according to the natural stress profile. The possibility of interactive diversion through convective settlement is also studied.
Effective Hydraulic Fracture Length and the Determination of Productivity Index
Authors: Malekzadeh Dariush , Khan Farid U. , Day John J.
Published: December 2007

This paper presents a new technique for analyzing the performance of hydraulically fractured vertical wells in bounded reservoirs. The main objective is to present a new set of practical equations, based on the recently introduced concepts in well testing, for evaluating the effective length of the hydraulic fracture contributing to unrestricted production. It is determined that the performance of a hydraulically fractured vertical well with mechanical skin and fracture half length Xf1 can be substituted by the performance of a fractured half-length Xf2 with no skin. New equations presented in this paper can be used to determine pseudo skin factor, effective fracture half-length, mechanical skin factor, shape factor, and productivity index of fractured vertical wells. The new equations and guidelines given in this paper can be used to determine the magnitude of formation damage around hydraulically fractured vertical wells and to evaluate the success of the stimulation treatment. An example based on simulated well test data is presented to illustrate the application of the new technique. The problems associated with the use of the finite-conductivity fracture model are discussed and it is recommended that the pressure transient data obtained on fractured vertical wells be analyzed with effective hydraulic fracture length concept, in preference to the finite-conductivity fracture model.
Research on Energy Balance Test of ESP
Authors: Zhen-hua Cui , Jun Zhu
Published: December 2007

Electrical Submersible Pump (ESP) is a kind of important means in the oilfield mechanical recovery. People used to place the emphasis on calculating the energy losses of every component by piece in the applications, and no test data were established.

This paper takes ESP as a system, and gives theoretical analysis on the energy losses of every ESP component. Energy balance test of ESP system is performed in test well for the first time, the pattern of energy-loss distribution is found and some proposals on improving the design, manufacture and application of ESP system are put forward. In addition, the test procedure and calculating method of energy losses for ESP system is offered.
Interference Test Analysis in Naturally Fractured Reservoirs
Authors: Ma Q. , Tiab D.
Published: December 2007

The directional flow properties of a reservoir are very important for the design of reservoir development and waterflooding. For a reservoir with natural fractures, the permeability is controlled by the preferred orientation of the fractures. This paper presents the results of an investigation for determining the fracture orientation from interference tests. The pressure response is analyzed based on the double porosity model proposed by Warren and Root. The calculations are performed numerically by use of Stephest Laplace inversion transform. The results show that the transition flow period depends not only on the fracture flow parameters, but also on the distance between the observation well and the active well. Based on this characteristic, a new method is presented to determine the fracture orientation and permeability components as well as the fracture-flowing parameters.
A Lithology Independent through Casing Porosity and Water Saturation Model LIPS
Authors: Oraby M. E.
Published: December 2007

The demand for low cost but reliable technology in drilling, logging and production is always and will continue to be one of the most important issues facing the oil industry. In addition, increasing production through field management and evaluating bypassed reserves in existing fields using lower cost but reliable technology is a primary objective of any oil company. From this motivation, a through casing log interpretation technology for assessing formation evaluation and identifying existing field opportunities would offer a low cost and risk option for many operations.

In this paper, a through casing log interpretation technology termed Lithology Independent Porosity and water Saturation or, LIPS, is presented. LIPS is a technology that is suitable for infill drilling programs, fluid monitoring for field management and in analyzing old fields that do not have enough or modern data. LIPS requires three measurements to provide porosity, water saturation and the locations of the heavy minerals that may be the source for net pay determination. These three measurements can be obtained using the three common cased hole logs; a thermal Compensated Neutron porosity Log or CNL, an epithermal neutron porosity and a Pulsed Neutron Capture log PNC type tool, e.g., TDT, for formation absorption cross section.

For porosity, LIPS considers any formation as a composite of two major components, the pore space and the matrix. LIPS deals with the matrix as a black box where it calculates its overall controlling parameters. The formation porosity is chosen when the calculated parameters using two different techniques converge.

For water saturation, LIPS uses data that has been discarded by the industry, the thermal neutron detectors counting rates of the thermal neutron tool. These counting rates are functions of the formation water salinity and the matrix absorption cross section. LIPS uses the two thermal neutron counting rates, near and far, of the thermal neutron tool CNL along with the formation absorption log to produce three equations in three unknowns. The three unknowns are water saturation, water salinity and matrix absorption. Therefore, LIPS does not require prior information about matrix absorption or the formation water salinity which gives LIPS superiority to many of the existing water saturation models.

LIPS has been tested in a variety of reservoirs from all over the world. Comparisons between LIPS porosity and water saturation and core porosity and low invasion water saturation core are presented. Also, the environmental effects on LIPS interpretations, e.g., invasion, are discussed.
Optimizing Water Injection Profiles with Oxygen Activation Logging
Authors: Schnorr D. R.
Published: December 2007

Impulse oxygen activation logging was successfully introduced in Alaska in 1990. It was immediately used to determine water injection profiles behind tubing in the annulus between the tubing and casing. In the past, this type of well completion was difficult, if not impossible, to evaluate with the techniques that were available before the introduction of the impulse oxygen activation logging method. The impulse oxygen activation technique uses the pulse neutron tool to activate the oxygen in the water so that the water flow profile can be determined. Since neutrons are used to activate the oxygen in the water, the metal in the tubing does not stop the activation of oxygen in the water when it is behind tubing. Impulse oxygen activation logging is also used to identify water producing zones in producing wells, and whether there is water flowing through channels in the cement behind casing.

This new method of using impulse oxygen activation provides the capability to trace water flow over a wide range of water injection and production rates. Using a series of station measurements, it is possible to measure water velocities from less that two ft/min (0.01 m/s) to more than 400 ft/min (2.0 m/s) with modified pulse neutron tools. The impulse oxygen activation method also has the ability to measure two different water velocities in the same direction at the same time. This is possible because only a small amount of water is activated by the impulse oxygen activation. The activated water then flows past three different detectors spaced at 2-ft, 6-ft, and 20-ft at its different velocities. Knowing the cross sectional areas of the different flow paths, water flow rates from l0 to over 10,000 BWPD are directly calculated. Since the pulse neutron tool has no moving parts, it cannot be plugged with scale or particles suspended in the injected water such as is the case with spinner type tools.

This measurement has significantly reduced the traditional uncertainties associated with the economics of attempting to shut-in high watercut intervals. With these advances the emphasis can now turn to assessing improved modification techniques. The final result will be increased oil recovery and reduced water cycling.
Laboratory and Field Evaluation of Organosilane as a Formation Fines Stabilizer
Authors: Stanley F. O. , Ali S. A. , Boles J. L.
Published: December 2007

Formation damage associated with fines migration has often contributed to rapid production declines and short-lived stimulation successes. Although clay migration and stabilization have been discussed in various papers through the years, the non-clay siliceous fines stabilization has received little attention. A recently developed fines stabilizing method is utilized to reduce or prevent the migration of both clay and non-clay siliceous fines. This method utilizes an organosilane additive which reacts in situ to stabilize potentially mobile siliceous fines. This paper describes the use of and the mechanism by which the organosilane additive stabilizes fines. The laboratory data and field case histories further discuss the beneficial effects of employing organosilane as a fines stabilizing agent.
A New Long Stroke Pumping Unit with High Speed
Authors: Wang D. F. , Cui X. M. , Gao G. Y. , Huang Z. Z. , Hu B. Z.
Published: December 2007

‘Qing You’ long stroke pumping unit is a high velocity pumping unit. It is designed to achieve a large pump output of more than 200 m3/d with the diameter of rod pump less than 70mm, and the aunulus test can be conducted in the course of production.

Based on the analyzing of some pumping unit commonly used in oil field and the relationships between acceleration and various parameters, in this paper, the design considerations was presented. The maximum velocity υm of the new developed pumping unit is about 40% higher than the recommendation for υm of common pumping unit, and its maximum acceleration αm is in the range of that of the conventional ones.
Beam Pump Balancing Based on Motor Power Utilization
Authors: McCoy J. N. , Ott R. E. , Podio A. L. , Collier Forrest , Becker Dieter
Published: December 2007

Recent application of a portable computer-based instantaneous power meter which is easily connected to a beam pump's switch box, has made it possible to study in detail the effect of counterbalancing on electrical consumption and operating cost.

This paper describes the measurement system as well as its application to determine the power usage per pump stroke and the gear reducer torque. A simple algorithm is presented for the determination of the counterweight adjustment required to modify the peak torque or the power use.

The results of accurately monitored field tests for a variety of beam pumps and well depths are presented in detail. The measurements indicate that unit balancing based on instantaneous power, yields results similar to those obtained from torque derived from dynamometer measurements using a horseshoe type load transducer. The ease of installation of the power probes compared to installation of the dynamometer makes this the preferred method for most beam pumping systems powered by electrical motors.
Using Automation for Optimizing Production Fields
Authors: Outomuro M. Vázquez
Published: December 2007

Through automation it is possible to remotely monitor and control production fields seeking to guarantee maximum production, minimum operating cost, and extending the useful life of the equipment.

The objective of the Automation scheme shown in this work consists of integrating all the steps needed to optimize a well through advanced control techniques that would comprehend three modules; a) Automatic Acquisition of Data (Field Instrumentation and Acquisition Systems); b) Real Time Data Processing and Issuing of recommendations (here we have Mathematical Modeling, Real Time Expert Systems, Neural Networks, Genetic Algorithms, Simulation Models); c) Control over field variables, allowing the application of the recommendations obtained in b)
An Approach to the Optimum Design of Sucker-Rod Pumping Systems
Authors: Han Dianli , Wiggins Michael L. , Menzie Donald E.
Published: December 2007

Sucker-rod pumping system design is often a trial and error process. Many simplifying assumptions are used which may not be consistent with the well conditions. This paper presents a new methodology for the optimum design of pumping unit systems.

In this approach, plunger diameter, polished rod stroke length, pumping speed and pump intake pressure are chosen as basic design variables. Production rate and rod string taper are determined by an iteration algorithm which systematically couples well inflow performance and vertical flow effects into the design process. Polished rod load, peak gear box torque, polished rod horse power and counterbalance effect are also determined at the end of the iteration calculation. Different design objective functions can be used to rate the pumping modes. Thus, the optimum design of pumping unit systems becomes a matter of solving for the combination of the four basic design variables which maximize or minimize an objective function within the limitations of available equipment by a mathematical programming method.
Single-Trip Completion Concept Replaces Multiple Packers and Sliding Sleeves in Selective Multi-Zone Production and Stimulation Operations
Authors: Coon Robert , Murray Doug
Published: December 2007

In conventional multi-zone completion operations, selective production and/or stimulation requirements are accomplished by opening and closing sliding sleeves in each producing zone. This completion method requires at least one trip per zone as well as substantial amounts of equipment in the well. An alternative method that is being field tested will move the internal control of the well from the tubing string to the casing. This eliminates equipment from inside the well and reduces the number of trips required from one per zone to a single trip for the entire well. This paper describes the single-trip completion concept, primarily for horizontal wells, as well as the new technology that has been developed to support it.
Transient Aspects of Unloading Oil and Gas Wells With Coiled Tubing
Authors: Gu H.
Published: December 2007

Unloading oil and gas wells with coiled tubing (CT) conveyed nitrogen circulation is a transient process in which the original heavier fluid in a wellbore is displaced by nitrogen and lighter reservoir fluid. The transient aspects need to be considered when determining nitrogen volume and operation time for unloading a well. A computer wellbore simulator has been developed and used to study the transient effects. The simulator includes transient multiphase mass transport and takes into account the different fluids in the wellbore and from the reservoir. The simulator also includes the gas rise in the wellbore liquid below the CT and can be used for gas well unloading. The transient results of oil and gas well unloading are presented. The effects of CT size and depth, workover fluid, and nitrogen rate and volume on unloading are discussed. Unlike continuous gas lift, the total gas volume needed and the operation time in an unloading process can only be determined and optimized based on a transient analysis.
Current Use of Limited-Entry Hydraulic Fracturing in the Codell/Niobrara Formations—DJ Basin
Authors: Eberhard M. J. , Schlosser D. E.
Published: December 2007

In the last several years, limited-entry perforating has been used for hydraulically fracturing the Codell and Niobrara formations in the Denver-Julesburg (DJ) Basin. Limited-entry perforating reduces stimulation costs with no apparent effect on production.

Several papers have presented guidelines for designing a limited-entry treatment. A primary concern for treating multiple intervals is to ensure that both zones receive the necessary treatment. Currently, some operators simply ratio the number of perforations in each interval to the volume of treatment required for each interval. To ensure that both zones are being treated, a minimum pressure drop of 700 to 1,000 psi is usually used for limited-entry design. Changes in the perforation discharge coefficient and diameter during the treatment, combined with changes in the net treating pressure, affect the perforation pressure drop calculation. To determine the actual pressure drop across the perforations, designers use a real-time spreadsheet calculation.

This paper reviews limited-entry treatments pumped in 34 wells that verify spreadsheet calculations. Changes in the perforation discharge coefficient and diameter will be presented, as well as the effect of proppant concentration and velocity through the perforation. The current spreadsheet calculation used on location to calculate the pressure drop across the perforations is also discussed.
Impact of Trapping of Residual Oil by Mobile Water on Recovery Performance Miscible Enhanced Oil Recovery Processes
Authors: Rampersad P. R. , Ogbe D. O. , Kamath V. A. , Islam R.
Published: December 2007

In this paper we examine how residual oil trapping by mobile water affects the recovery performance of miscible EOR processes. The objectives of the study are (1) to develop a multiphase, numerical model to investigate factors affecting water-blocking and the release of oil from dendritic states; (2) to evaluate performance of miscible processes and forecast displacement efficiency and recovery under a variety of operating conditions, and (3) to determine the "optimum" water-solvent ratio to be used in a miscible Water-Alternate-Gas (WAG) process. Using the multiphase flow model, we considered the oleic phase as two parts, a mobile phase and a trapped phase, and studied the effects of capillary forces, solvent viscosity, fraction of trapped oil, dispersion and mass transfer coefficients on recovery performance. Guidelines for determining the optimum water-solvent ratio to be used in a miscible WAG process are discussed.
Fracturing from Highly Deviated and Horizontal Wells: Numerical Analysis of Non-planar Fracture Propagation
Authors: Olson Jon E.
Published: December 2007

Fracturing from horizontal and highly deviated wells can often result in complex, non-planar fracture geometry. A two-dimensional model was developed to analyze the effects of non-planar fracture propagation for different in situ boundary conditions and hydraulic fracturing parameters. Numerical simulations show that curving fracture geometry reduces created fracture length compared to a planar fracture and causes a fracture width restriction at the wellbore. Reduction in fracture length can reduce expected well stimulation effects and jeopardize well economics. Near-wellbore width restrictions increase fracture treating pressure and may cause wellbore screen-out during the proppant stages of a fracturing treatment. The negative impact of non-planar geometry can be mitigated with short perforated intervals, high viscosity fracturing fluids, proper wellbore alignment and pre-pad proppant slugs for near-wellbore erosion.
Forecasting Long-Term Gas Production of Dewatered Coal Seams and Fractured Gas Shales
Authors: Spivey J. P. , Semmelbeck M. E.
Published: December 2007

A procedure is presented which allows forecasting long range performance of dewatered coal and fractured gas shale reservoirs having nonlinear adsorption isotherms, using constant pressure solutions to the flow equation for slightly compressible liquids. A correlation is presented to show the range of applicability of this procedure.
Computational Modeling of Multi-Layered Reservoirs With Unequal Initial Pressures: Development of a New Pre-Production Well Test
Authors: Aly Ahmed , Lee W. J.
Published: December 2007

The objective of this paper is to present a description and verification of a new semi-analytical simulator used to model the wellbore performance of multi-layered reservoirs with unequal initial pressures. The semi-analytical simulator proved to be faster than a conventional three-dimensional, finite-difference commercial simulator. Also the amount of information needed to run the model is much reduced. The semi-analytical simulator allows each layer to have different layer properties, different boundary conditions, and different initial pressures.

The semi-analytical simulator was used to model the reservoir performance for two, three and five layered reservoir cases from the literature. The results were verified by comparing them to the results generated using a finite-difference simulator. The agreement was excellent for all the tested cases.

Also, we developed a new well test, the Pre-Production Well-test or PPWT. The PPWT is performed early in the life of a reservoir when the information is most needed for planning production schedules and making economic decisions concerning the life of the wells. Pre-production is the period after completion but before production of the well. Immediately after perforation, we position a pressure gauge above the top perforation to measure the pressure performance from the total system (in two or three layer systems). Cross flow in the wellbore from one layer to another will cause the pressure signal. The cross flow is due to the differential pressure between the layers. One important advantage of the pre-production well test is that there is no production on surface during the test. Thus, the environmental impact caused by flaring oil or gas during a conventional well test is alleviated.

We developed the "Derivative Extreme Method" (DEM) for the analysis of wellbore pressures measured during the pre-production well test. The DEM determines layer properties form single pressure profile; no rate measurements are required. The DEM requires that the wellbore pressure be measured until one boundary is felt (i.e., the late-transient region must be reached).
Comparison of Single and Multi-Facies Variograms of Newcastle Sandstone: Measures for the Distribution of Barriers to Flow
Authors: Lund H- J. , Ates Harun , Kasap Ekvem , Tillman R. W.
Published: December 2007

The objective of this paper is to quantify the distribution of potential flow units within valley-fill outcrop deposits by utilizing geostatistical parameters, especially variograms. The Newcastle (Muddy) Sandstone, which is a prolific producer in the Powder River Basin of Wyoming, is the subject of our outcrop reservoir characterization analysis which compares the relationships of detailed geological (sedimentological) interpretations of facies, detailed in situ permeability measurements, and outcrop gamma-ray log surveys. Much of the Newcastle (Muddy) Sandstone, which crops out near Newcastle, Wyoming was deposited by tidal currents backfilling valleys formed during a Lower Cretaceous sea level drop. The Skull Creek Shales which underlies and is lateral to the Newcastle sandstone forms lateral and bottom seals.

We concurrently measured the permeabilities and gamma-ray responses of beds on three vertical transects with a grid extending normal to the bedding and three lateral grids which are as nearly parallel to the bedding as possible. We generated geostatistical parameters from these data sets. In all cases, Dykstra-Parsons coefficients are in the neighborhood of 0.35 for the single-unit data and above 0.8 for the multi-unit measurements. Coefficients of variation are below 0.5 for single units and above 0.8 for multi-unit data sets.

Multi-unit variograms show hole effect and often strong trend, while single unit variograms always indicate nugget effect with a weak trend. The correlation between the plots generated from measured permeability and gamma-ray responses are impressive. Permeability and gamma-ray variograms are similar. The variograms in the vertical and horizontal directions are quite different. Therefore, they cannot substitute one for another. We also concluded that relative semi-variograms are a better way of presenting formation heterogeneities. We observed that abrupt variations in outcrop gamma-ray values are also excellent indicators of bed contacts.

We used the generated geostatistical parameters in a simulated annealing program to predict permeabilities of lateral profile A, and concluded that variogram, mean and standard deviation are required but not sufficient parameters to predict the distribution of reservoir heterogeneity.
Interpretation of Steam Drive Pilots in the Belridge Diatomite
Authors: Johnston R. M. , Shahin G. T.
Published: December 2007

The South Belridge Diatomite Field contains more than 2.5 billion barrels of oil-in-place. Current primary and waterflood development are estimated to recover only a small fraction of this oil. Despite it’s low permeability, the diatomite may be a good candidate for the steam drive process, due to its thick oil column (1,000 ft), high porosity (50% to 65%), and high oil saturation (up to 70%).1 With these attributes, thermal expansion and decreased viscosity of reservoir fluids accelerate oil production, without significant heat loss to cap and base rock.

Steam drive pilot operations have been conducted at South Belridge since 1986. This paper discusses the pilot projects and the 15-acre steam drive full-scale project currently being installed.
Hydraulic Fracture Orientation and Production/Injection Induced Reservoir Stress Changes in Diatomite Waterfloods
Authors: Wright C. A. , Conant R. A. , Golich G. M. , Bondor P. L. , Murer A. S. , Dobie C. A.
Published: December 2007

Waterflooding of California’s diatomite reservoirs has been extensively employed for two reasons: (1) to increase total recovery, and (2) to mitigate the potentially catastrophic effects of reservoir compaction and the resulting surface subsidence. Waterflooding has typically striven to replace each barrel of produced fluid with a barrel of injected water in order to achieve "zero net voidage". The extremely low permeability of the diatomite reservoirs, however, results in the generation of very significant reservoir pressure gradients during waterflooding, even under zero net voidage conditions. These extreme gradients in reservoir pressure, together with the reservoir compaction, result in significant changes in the local reservoir stress field. These local stress perturbations can, in turn, result in reorientation of hydraulic fractures on infill wells and possibly contribute significantly to the potential for wellbore casing failure.

This paper summarizes the (preliminary) findings from extensive field studies of hydraulic fracture orientation in diatomite waterfloods and related efforts to monitor the induced surface subsidence. Included are case studies from the Belridge and Lost Hills diatomite reservoirs. The primary purpose of the paper is to document a large volume of tiltmeter hydraulic fracture orientation data that demonstrates waterflood-induced fracture reorientation—a phenomenon not previously considered in waterflood development planning. Also included is a brief overview of three possible mechanisms for the observed waterflood fracture reorientation. A discussion section details efforts to isolate the operative mechanism(s) from the most extensive case study, as well as suggesting a possible strategy for detecting and possibly mitigating some of the adverse effects of production/injection induced reservoir stress changes — reservoir compaction and surface subsidence as well as fracture reorientation.
Coiled Tubing Deployment of 3.5 " Tubing To Be Used As Offshore Gas Pipeline
Authors: Mabry Sam , Walker Rohan , Benge Carl
Published: December 2007

In the past innumerable pipelines, both onshore and offshore, have been replaced by a variety of methods. These have ranged from replacement of the pipeline to a sliplining of it by different means. These methods have different advantages and disadvantages due to the circumstances in which it is implemented. Several have environmental drawbacks and others suffer as a result of the large amount of equipment and personnel required to perform them.

In order to minimize the time required to install a replacement gas pipeline SWEPI investigated the possibility of using coil tubing for this application. Upon presenting the scenario to Schlumberger Dowell the project left the realm of conjecture and began to be viewed as a viable option .

The project consisted of the installation of one 3.5″ coil tubing slip liner and two communications cables in the existing 8″ gas production pipeline from SWEPT s Platform Emmy to the onshore receiving area at SWEPI's Huntington Beach Production Unit, Huntington Beach, California.

This paper details the operational and design considerations that were involved in the project and illustrates one of the methods that have caused coil tubing to be such an innovative and indeed integral segment of well servicing.
Total Well Management - A Methodology for Minimizing Production Cost of Beam Pumped Wells
Authors: Podio A. L. , McCoy J. N. , Becker Dieter
Published: December 2007

A procedure is described that allows an operator to identify those beam pumped wells which are operating at reduced efficiency. The logical sequence of steps to be followed in acquiring performance data such as power, dynamometer, fluid level, etc. and the criteria to be used in determining the causes of inefficiency are presented with the objective of reducing the time and effort required to perform the analysis.
An Application of Crosswell Tomography Using a Hydrophone Receiver Array to Monitor Steam Migration in an Unconsolidated, Heavy-oil Sandstone, West Coalinga Field, California
Authors: Blevens D. M. , Fairborn J. W.
Published: December 2007

Two crosswell tomography surveys were conducted in the vicinity of a new infill steam injector with the primary objective of monitoring steam (heat) migration within a thick, unconsolidated, heavy-oil, sandstone reservoir. The crosswell tomography detected heat-induced velocity decreases between the two surveys, the first conducted just before steam injection and the second conducted approximately three months later. Difference plots from the two surveys clearly define areas with temperature change and contact temperature logs corroborate the zone of peak change. The crosswell tomography data and the inferred steam migration characteristics halted an operational strategy for the steam drive and were later a factor in the abandonment of continuous steam injection.

The second objective of the crosswell tomography project was to demonstrate the viability and cost-reduction benefits of a hydrophone receiver array in an unconsolidated reservoir. This project represents one of the first applications of hydrophone receivers in such an environment. Data quality from the hydrophones proved adequate for first-arrival (P-wave) tomography although, it is likely reduced from that obtainable with geophones. As a benefit, acquisition costs for this trial were dramatically less than estimates using geophones.
Video Camera Log Used for Water Isolation in the Main Body "B" Pool, Elk Hills Field, Kern Co., California-Water and Oil Identification
Authors: Starcher M. G. , Murphy J. R. , Alexander P. D. , Whittaker J. L.
Published: December 2007

The Main Body ’B’ reservoir in the Elk Hills Field is a peripherally waterflooded, +400’ thick series of layered, turbidite Stevens sands. Permeability variation between layers adversely affects the vertical sweep, resulting in production from lower permeability oil sands dominated by production from higher permeability sands. This paper discusses the unique use of various tools to identify water zones to isolate and oil zones to stimulate. Tools used to identify water and oil entry are discussed with respect to their capabilities of identifying oil and water entry into the wellbore.

Swept and unswept layers are identified and the confidence level to propose a water isolation remedial has been developed; The confidence level is based on the analysis of a video camera log, open hole logs, production logs and production tests. This analysis begins when a candidate well with a high water cut is shut in, and the afterflow is viewed with a video camera. Oil entry is identified and evidence of water entry is inferred. These observations are compared with results from production tests in offsets, electric logs showing processed layers in an offset redrill, and production logs, and a video camera log from the same well. Agreement in the data provides the confidence level regarding what zones to isolate as watered-out and what zones will produce economic oil rates after the remedial.

If results from water isolation remedials are available, these results may also be reported.
Field Test of Acoustic Logs for Measuring Porosity and Oil Saturation in a Mature Waterflood in the Wilmington Field, CA
Authors: Moos Daniel , Hara Scott , Phillips Chris , Hooks Andrew , Tagbor Kwasi
Published: December 2007

A field test was carried out in the Wilmington Field, CA. to assess the effectiveness of multi-pole acoustic logs to measure porosity and oil saturation through casing in sands waterflooded for over 40 years. The field test was also designed to assess the production potential of selectively recompleting wells in high water cut areas. The multi-pole acoustic logs offer a promising new method for reservoir characterization, depletion monitoring, and optimizing the recomplete and redrill potential of existing wells. The Department of Energy (DOE) is co-funding a multi-year study to refine the acoustic log analyses, to improve reservoir characterization, and to evaluate the cost effectiveness of various recomplete methods.
A New Semi-Analytical Model for Thermal Recovery Processes
Authors: Pooladi-Darvish Mehran , Tortike W. S. , Ali S. M. Farouq
Published: December 2007

Gravity drainage of heated oil in thermal recovery processes is an important mechanism, often resulting in high sweep efficiency with economical rates. A semi-analytical model is developed to predict production rate from heavy oil reservoirs under non-isothermal gravity drainage. This work improves upon the previous ones by accounting for the unsteady-state effects in the heat flow process as well as considering the effect of the moving interface, in cylindrical coordinates. The solution incorporates a Heat Integral Method (HIM) to approximate the 2-D heat transfer in the reservoir. The shape of the oil-steam interface is found as a part of the solution. The predictions of the model are validated against published experimental results. Examples for two Californian heavy oil reservoirs indicate that economical rates with high sweep efficiencies can be obtained from reservoirs under gravity drainage, especially when the surface area of the production well exposed to the reservoir is increased, e.g. by implementing horizontal producers.
A Performance Incentive Contract That Pays Off For All Parties
Authors: Krummrich C. R. , Johnston R. E. , Crist T. W.
Published: December 2007

The Western Business Unit Bakersfield drilling department of Chevron, U.S.A. Production Company developed a drilling performance incentive contract that was implemented during 1994 in the Lost Hills field of California. The performance incentive contract (PIC) financially rewarded all of the drilling contractor’s rig employees for outperforming pre-established drilling performance goals.

The key elements of the performance incentive program are: 1) Goals that trigger incentives are based on cost categories that are controllable by the drilling team; 2) Goals were established using a database of past years performance; 3) Goals that are not achieved negatively impact the incentive earned in an effort to deter repeated errors; 4) Accidents that occur on the job negatively impact the incentive earned; 6) Administration of the program is not time consuming.

The results of using an incentive contract in the Lost Hills drilling program are; 1) Time and cost of operations are reduced; 2) The results are measurable and repeatable; 3) A team environment develops in which ideas are shared and acted upon by crew members and supervisory personnel.
Blowdown Optimization for the East Coalinga Extension Field, Coalinga Nose Unit Fresno County, California
Authors: Starzer Michael R. , Tenzer Jeffrey R. , Larson John W. , Bunch Bruce C. , Boehm Mark C.
Published: December 2007

This paper will review recent value optimization strategies associated with gas cap blowdown of the East Coalinga Extension Field, Coalinga Nose Unit, Fresno County, California. In addition to forecasting the ultimate recovery under differing blowdown rates and timing, cost of production, market factors and split stream analyses were employed to develop an optimal blowdown scenario. This paper will also review the latest efforts to increase value including the pursuit of investment opportunities, a restructuring of operations and the cessation of the NGL product stream. These efforts during the past few years have resulted in lowering lift cost to less than two dollars per barrel oil equivalent, the lowest cost for California oil fields producing greater than 1000 barrels of oil per day.1

The Coalinga Nose Unit development is jointly owned by four companies: Unocal (operator), Texaco, Mobil and Chevron. Approximately 466 million barrels Of oil have been recovered from the field which is now producing 1,200 barrels of oil and 60 million cubic feet of gas per day from the Gatchell Member of the Lodo Formation. Recovery from the field has been influenced principally by gravity drainage, gas cap expansion, aquifer withdrawal and gas re-injection. Since unitization in 1950, over 1 trillion cubic feet have been produced, the majority of which have been re-injected into the gas cap to maintain reservoir pressure. Water withdrawals of 460 million barrels from the regional aquifer have successfully limited encroachment into the oil band. Gas re-injection, control of aquifer encroachment and favorable reservoir characteristics for gravity drainage have resulted in ultimate recovery approaching 60 percent of original oil in place.
Development Planning and Reservoir Management in the Duri Steam Flood
Authors: Gael B. T. , Gross S. J. , McNaboe G. J.
Published: December 2007

The overall objective of reservoir management and development planning for the Duri field is to maximize project value. Key elements of Duri's reservoir management practices include: injecting steam in new patterns at rates up to about 1.2 BCWEPD/NAF* or the maximum rates achievable below fracture pressure; distributing the steam into reservoir layers in proportion to their h𝜙So; maintaining these rates until steam breakthrough occurs in multiple wells in a pattern; then performing injector wellwork to shift steam out of the breakthrough layers while continuing initial rates into the non-breakthrough layers. The area-wide rate reduction schedule caused by these shifts resembles a heat balance (Vogel1) rate reduction schedule. The steam that is shifted out of an old steamflood development area becomes the supply of steam for the start up of a new area. Key elements of Duri's development planning practices include: obtaining sufficient reservoir information to be able to predict performance of all areas in the field; dividing the undeveloped parts of the field into steamflood areas that are logical and will fit the steam availability and construction scheduling constraints of the project; ranking the new projects by their profitability; and installing them at a schedule that matches the steam shifts out of the old areas with the ramp up of the new area so that steam plant capacity is fully utilized. This paper discusses the interrelationships between reservoir management practices, development planning, and the maximization of overall DSF project value.
Diagnosis and Prevention of Norm at Eugene Island 341-A
Authors: Shuler P. J. , Baudoin D. A. , Weintritt D. J.
Published: December 2007

We conducted a field study at Eugene Island 341-A to develop guidelines for the cost-effective prevention of NORM (Naturally Occurring Radioactive Materials).

The specific objectives of this study are to:

determine the root cause of the NORM problem at this facility, using a wide variety of diagnostic techniques. consider available engineering options to prevent NORM from forming. determine the most cost-effective engineering solution.

An overall objective is to generalize the results and diagnostic techniques developed for Eugene Island 341-A to other production facilities, especially in the Gulf of Mexico.

This study shows that the NORM problem at Eugene Island 341-A stems from mixing incompatible produced waters at the surface. Wells completed in Sand Block A have a water with relatively high barium concentration, those in Sand Block B and C are high in sulfate. When these waters mix (starting in the production headers), barium sulfate forms. Radium that is present in the produced brines co-precipitates with the barium, thus creating a radioactive barium sulfate scale deposit (NORM).

The barium sulfate (and hence NORM) can be prevented by improving the current scale inhibition program. Keys to an effective program are the continual, reliable injection of ah appropriate scale inhibitor at an effective dosage, ahead of the point where scaling conditions begin.