bluuebunny/crossref_metadata_2025 huggingface dataset:
Diamond-Enhanced Insert: New Compositions and Shapes for Drilling Soft-to-Hard Formations
Authors: Keshavan M. K. , Siracki M. A. , Russell M. E.
Published: December 2007

Increased penetration rates, accompanied by longer bit life, have always been primary objectives of both rock bit manufacturers and drilling contractors. Diamond-enhanced tungsten carbide inserts have been employed successfully in the gage row of soft formation three-cone rock bits. However, the current semi-round top geometry used in the manufacture of diamond-enhanced inserts has limitations. Two such limitations are slower penetration rates when replacing chisel-type gage inserts in certain soft formations and premature breakage in medium-to-hard formations (IADC 6-2-7 to 7-3-7 type drilling). This paper reviews recent progress in the development of tougher diamond-enhanced inserts and new geometries, such as the inclined chisel gage inserts.

Laboratory test results are compared between the new, tougher enhanced inserts, the standard enhanced inserts and the standard tungsten carbide grades. Successful field tests of diamond-enhanced heel inserts used in medium-to-hard formations will be reviewed. The impact on bit life, penetration rates and drilling costs of the new enhanced insert composition and geometry technology also will be discussed.
The Effects of Asymmetric Nozzle Sizing on the Performance of Roller Cone Bits
Authors: Wells M. R. , Pessier R. C.
Published: December 2007

A major factor governing the performance of roller cone drill bits is the efficiency with which the drilling fluid removes rock cuttings (and fines) generated beneath the bit. Traditionally, the hydraulics at the bit has been optimized by expressing the losses in the circulating system as a function of flow rate then maximizing either horsepower at the bit or impact force without regard to the position and size distribution of the nozzles.

This paper describes results obtained using a novel technique where the hydraulic cleaning and scouring of the bottom of borehole is optimized by using an Asymmetric Nozzle Sizing procedure. Unlike the conventional practice of uniform nozzle sizing, this procedure combines a single large nozzle with two smaller nozzles. The jetting action of the larger nozzle enhances the crossflow component of the global flow pattern and greatly intensifies the turbulence levels beneath the bit.

A series of laboratory experiments is discussed showing that turbulent fluctuating pressures measured along the hole bottom beneath a roller cone bit are significantly more intense and cover a larger area when using the asymmetric nozzle arrangement than when using conventional, uniform or equal size nozzles. In addition, the asymmetric nozzle configuration is shown to produce a substantial cross flow along the bottom of the borehole. The combination of intense turbulence and cross flow greatly enhance bottomhole scouring.

Finally, the results of a series of full scale laboratory drill tests are presented that quantify the advantage of asymmetric nozzle sizing and the need for increased hydraulic horsepower and bottom hole turbulence at greater depth. These results indicated an increase in the rate of penetration (ROP) on the order of 20% using the asymmetric nozzle sizing technique over that measured using conventional, uniform nozzle sizing. In addition, field tests results are provided that indicate similar or greater increases in ROP, longer bit life and greater savings (cost per foot) were achieved using asymmetric nozzle sizing.
The Role of Contingencies in Incentive Bid Preparation
Authors: Moy M. A. , Kent D. J.
Published: December 2007

A different bidding strategy must be adopted by the Drilling Contractor when bidding for incentive contracts as opposed to normal dayrate contracts, if expected reward to be gained is to be equated to the additional risk taken during incentive operations. Risk analysis, in relation to expected or perceived drilling problems and which in turn are part of the Contractors contractual liabilities, is essential in all incentive type contracts. Based upon such an analysis the Drilling Contractor must then decide whether to accept the proposed contractual risk allocation, include contingencies in the price, make contractual exceptions, take out insurance to cover the risk assumed, or adopt any combination of the aforementioned solutions. This paper addresses risk analysis in relation to the risk-reward scenario, and suggests a methodology /procedure for assessing and calculating the risk when preparing incentive bid proposals.
Superior Performance With Minimal Environmental Impact: A Novel Nonaqueous Drilling Fluid
Authors: Friedheim J. E. , Pantermuehl R. M.
Published: December 2007

The first well utilizing a novel drilling fluid based on polyalphaolefin (PAO) chemistry has been drilled in the North Sea. In addition to excellent drilling performance, PAO drilling fluids exhibit low toxicity, low bioaccumulation, and are biodegradable. Success of the PAO mud has established the system as a viable synthetic-based alternative to oil-based muds.

The non-aqueous PAO system was used to drill the 12.25-in. section of a well in the Central Basin of the North Sea. The interval from 6,300 to 15,067 ft (1,920 m to 4,592 m) was drilled at an angle of 55 deg. The formation consisted primarily of tertiary shales mixed with limestone stringers. Mud weight range was 15.0-15.5 ppg (1.8-1.86 s.g.).

Comparisons with oil-based muds used in this area of the North Sea indicated the PAO fluid helped increase penetration rates and reduce torque and drag. Other performance benefits included superior hole cleaning and no evidence of weight material sag. Additionally, cuttings discharged into the sea retained an average of less than 10% PAO (<100 g/kg dry retort solids).

Comparisons with other non-aqueous alternatives such as ester and ether-based fluids show PAO systems provide better elastomer compatibility, lime and cement tolerance, surface handling, synthetic/water ratio flexibility, and temperature stability.

This paper covers drilling and fluid performance results of the first field trial of a PAO-based mud. Environmental data including toxicity, bioaccumulation, and cuttings beds studies also are discussed. Chemical and practical differences between PAO and other synthetic-based muds are presented.
Fracture Mechanics Issues Relating to Cuttings Re-Injection at Shallow Depth
Authors: Willson S. M. , Rylance Martyn , Last N. C.
Published: December 2007

Re-injection of oil contaminated drill cuttings is attracting considerable attention as a cost effective means of complying with environmental legislation concerning discharges of drilling wastes. Gyda is the first North Sea platform to adopt this method as the sole means of disposing of its drilling wastes. The ground cuttings slurry (ca. 15,000 bbls per well) is injected via the 13 3/8" × 9 5/8" casing annulus into hydraulic fractures of up to 213m radius created in the mudstone formation at 900m depth.

Novel analyses using a 3D fracture simulator show that in the absence of stress or permeability barriers to prevent unconstrained height growth, fracture breakthrough to surface is theoretically possible if injected volumes exceed 90,000 bbls. The analyses further demonstrate that laterally extensive shallow sands do however provide effective permeability barriers to vertical height growth if injected volumes exceed 52,000 bbls.
An Improved Method for Grinding and Reinjecting of Drill Cuttings
Authors: Sirevåg Gunnar , Bale Arthur
Published: December 2007

A successful reinjection of oil-wet drill cuttings has been performed on the Norwegian Gullfaks Field. The reinjection was carried out in the annulus between two casing strings through a wear-protected wellhead. An effective way of grinding cuttings and mixing slurry by use of a new patent pending method known as SMACCC – Statoil Method for Autogenous Crushing and Classifying of Cuttings has been developed.

The paper discusses reservoir aspects and presents simulated fracture geometries as a result of rock mechanical and slurry in-put property data. Further, the paper describes a 1000 hour wear test, involved equipment, and gives a derived formula describing wear from sand slurries on internal wellhead components.
Present Methods of Drilling Process Analysis, Forecasting, and Control in Conditions of Insufficient Information
Authors: Mnatsakanov A. V. , Shirin-Zade S. A. S.
Published: December 2007

In many cases the technological processes of drilling wells, especially in exploratory drilling, are carrud out in conditions of insufficient information.

Shortage of information is connected with lack of data on geological features of the drilled area, rock physical, mechanical and rheological properties, with complexity and uncertainly of heat-mass exchange processes in the system "well-formation", drill pipes and casing interaction with rocks, bit interaction with boffom hole and so on. Besides, it should be noted, that the driller often deals with misrepresented initial information. It is in these conditions it is nessesary to investigate multicriterion complicated technological process of drilling and provide high effeciency of decisions made in conflict situations. Howether, the experience and intuition do not always provide the best choice in these conditions. The objective can be accomplished only on the base of complex approach to the procedure of making decisions and using the up-to-day methods of investigation of complicated and undefined systems.

In the paper, depending on the significance and complexity of the investigated technological process, different methods of making decisions in the conditions of insufficient information are considered.

For this, the principles of simulation, methods of indistinct sets, variation principles of mechanics, present achievements of dynamic systems theory are used.
An Analysis Accounting for the Combined Effect of Drillstring Rotation and Eccentricity on Pressure Losses in Slimhole Drilling
Authors: Cartalos Ulysse , Dupuis Dominique
Published: December 2007

Knowledge of the distribution of pressure losses is a key factor to the design of a slimhole well. However, predicting annular pressure losses-the major partis difficult because drillstring motion makes nonnegligible complex contributions that have not been accounted for up to now.

Flow in an eccentric annulus with eccentricity varying in the axial direction is studied. The effect of rotation induced transverse vibrations is included by allowing time periodic variations of eccentricity. The resulting model predictions can reproduce trends observed in field data.
A New Tool Joint Design Increases the Fatigue Life of Drillpipe Tubes
Authors: Wilson G.E.
Published: December 2007

SPE and IADC Member

Premature failures in drill pipe have plagued the drilling industry for a long time. These failures usually occur within two feet of the box and pin tool joints. Previous work has shown that most of these failures are the result of an abrupt internal taper (1/2" - 1-1/2" long) (12.7 - 38.1mm) and slip damage. New long taper upset designs have helped solve this fatigue problem. This paper discusses a new stress relief tool joint that greatly enhances the benefits of the new, long taper upset by almost doubling the fatigue life.

Introduction

Fatigue failures in drill pipe are caused by cyclic bending stresses. These stresses are concentrated in the thin wall section of the drill pipe where the thick upset blends into the tube. I believe drill pipe today is being subjected to higher and higher stresses with the advent of top drives, deeper wells and higher angle holes. This condition is further agitated by a more hostile environment with the increasing presence of H2S, CO2 and brine water. Therefore, I believe everything possible should be done to improve the fatigue life of drill pipe. Both the long taper upset and the new stress relief tool joint will help accomplish this.

REVIEW OF PROBLEMS AND PREVIOUS TEST WORK

I think the problem of drill pipe fatigue has been sufficiently defined. Many drilling contractors and oil operators along with the IADC and API have made studies of a vast number of failures, and most all of them pointed to an abrupt upset along with slip damage as being the problem. It has also been observed that rapid deterioration of the internal, plastic coating in this area compounds the problem.

P. 893^
Surface Measurement and Analysis of Drillstring Vibrations While Drilling
Authors: Macpherson J. D. , Mason J. S. , Kingman J. E. E.
Published: December 2007

Drillstring vibrations while drilling cause premature drillstring component and bit failure, and represent a waste of drilling energy. To increase drilling efficiency, drillstring vibrations are monitored and analyzed and the optimum drilling parameters and practices are determined as a well is drilled. This results in a reduction in the frequency of drillstring failures and the amount of time spent tipping and/or fishing, and an increase in both bit life and drilling rate.

This paper presents vibration signatures and analyses selected from over 15,000 hours of vibration data obtained using a surface vibration measurement sub. The case histories demonstrate the surface detection of drillstring resonance, BHA (Bottom Hole Assembly) lateral vibrations, PDC (fixed cutter) bit whirl, shock sub closure, torsional string oscillations, premature bit bearing failure and impending stuck pipe.
The Effect of Micro-Fractures on Oil Recovery From Low-Permeability Reservoirs
Authors: Perez J. M. , Poston S. W. , Edwards C. M.
Published: December 2007

The application of horizontal drilling has made exploitation of oil from low matrix permeability, naturally fractured reservoirs feasible. However, enhancing recovery from this reservoir type presents a distinctive problem. The low porosity and permeability matrix is virtually unaffected by the fluids injected into the extremely high permeability fractures. These fractures are multi-leveled and range from large scale macro-to small scale micro-fractures.

The effects that the presence of fractures on oil recovery due to water imbibition was studied. Both unadulterated and carbonated water imbibition tests were conducted on Indiana Limestone cores confined by a fluid pressure of 800 psi. Water was enriched with CO2 at a 500 psi carbonation pressure for the carbonated water cases. Magnetic Resonance Imaging (MRI) methods were used to study the effects that micro-fractures have on their surrounding rock matrix during oil production by water imbibition.

The presence of micro-fractures revealed that several factors may assist oil displacement: Capillary forces drive water into the microfracturesIncrease in the surface area available for water imbibitionOil trapped in fractures can be displaced by this process.An adequate wettability facilitates the process

Inclusion of CO2 improved oil recovery by: Increasing the oil mobilityA solution gas drive induced by the evolving CO2 when the system pressure is decreased below the carbonation pressure.

The presence of micro-fractures wide enough to allow appreciable fluid movement, increased oil production when compared to production from homogeneous rock. Imaging studies showed water channels were formed within the fracture system.

The presence of micro-fractures used the beneficial effects of capillary forces within the fracture system to create fluid paths that assist oil production. CO2 dissolved into the water being imbibed by the rock was found to accelerate oil recovery rates and increase ultimate oil recovery when compared to unadulterated water imbibition.
A New Simplified Compositional Simulator
Authors: Buchwalter J. L. , Miller C. A.
Published: December 2007

A new simplified fully implicit compositional simulator has been developed. This simulator is different from existing models because it combines the conventional black oil equations with a compositional injection component equation. The simulator runs at speeds that far exceed the speeds in current compositional simulators, primarily because the speed is independent of the number of components. Data preparation is both simplified and improved because component pseudoization is not needed. The simulator has been tested successfully for gas cycling projects including the Third SPE Comparative Solution Project and CO2 flooding projects.
Optimization and Evaluation of Openhole Cavity Completion Techniques for Coal Gas Wells
Authors: Logan T. L. , Mavor M. J. , Khodaverdian Mohamad
Published: December 2007

An innovative completion technique that has been used to effectively complete coal gas wells is an open-hole completion in which the coal is encouraged to slough into the wellbore. During the completion process, the wellbore is effectively linked to the reservoir due to the creation of numerous multi-directional self-propped fractures. The technique has been commonly called an "open-hole cavity completion." However, the cavity is a by-product of the process and not the primary objective of the completion. A more suitable terminology for the technique is "dynamic open-hole completion." The majority of the dynamic open-hole completions have been performed in the Fruitland Formation of the San Juan Basin, Colorado and New Mexico. Dynamic open-hole completed coal gas wells in some areas, but not all, produce at significantly greater rates than wells completed using other techniques such as hydraulic fracturing. Because of the success in the San Juan Basin, dynamic open-hole completions have been attempted in other basins including the Piceance, Powder River, Arkoma, Uinta, and Black Warrior. This paper presents a conceptual model and a working hypothesis concerning what takes place in the coal reservoir during the dynamic open-hole completion process. Based upon this model and hypothesis, techniques to: i) optimize the completion, ii) evaluate the effectiveness of the technique, and iii) how to determine when to terminate completion operations will be presented.
Drilling Successfully through Deforming Shale Formations: Case Histories
Authors: Talabani Soran , Chukwu Godwin , Hatzignatiou Dimitrios
Published: December 2007

Shale sloughing and swelling are the two major problems encountered when drilling through shale formations. Some areas are characterized by shale sections containing bentonite or other hydratable clays, which continually absorb water, swell and slough into the hole. These types of formations are known as heaving shales. This problem, if left uncombated, results in high cost of drilling the hole and significantly, to other hole problems (pipe sticking, excessive solid buildup in the mud and hole bridging), and sometimes abandoning the well because of the difficulty of reaching the targeted or anticipated pay depth. Drilling through shale formations can, many a time result to hole stability problems and may be aggravated the more when drilling through more than one kind of shale lithology.

The existing literature addresses possible solution techniques to combat the shale problems based on laboratory studies but these techniques neglect the existence of shale heterogeneities which may cause sloughing and swelling while drilling the same shale formation.

This paper examines the physical appearance of various shale samples with a view to (a) determining the physical properties which contribute to the shales' undesirable properties, and (b) proposing methods to minimize their effects on drilling performance. Five field cases are presented where sloughing and swelling shales were encountered. These cases reveal that the heterogeneity of the shale formations can cause difficulties in controlling the sloughing and/or swelling problems because of the variations in shale composition, ion exchange capacity, formation water content and shale strength.
Case History of Pressure Transient Testing at McElmo Creek, Utah
Authors: Shaw E. C.
Published: December 2007

This paper presents the results of a review of over eight hundred historical pressure tests conducted in the McElmo Creek Unit of southeast Utah. Three hundred pressure transient analyses were performed. The paper describes how this data base was used to characterize trends in pressure, reservoir quality and stimulation effectiveness. The various techniques used to acquire the pressure data are also discussed.
Special Aspects of Applying Constant Rate Analysis Approach in Low-Permeability Formations
Authors: Enachescu Cristian , Ostrowski L. P.
Published: December 2007

This paper describes special aspects and problems encountered when analysing transient pressure tests in low permeability formations. A constant rate approach has been widely used in oil and gas industry for analysing well tests. However, in low permeability formations special problems arise in applying the constant rate analysis method.

First, using the constant rate approach the pretest borehole history must be approximated. As it acts as a long term constant pressure injection or production event while drilling through the test interval it results in the creation of a non-uniform pressure distribution in the vicinity of the borehole. Numerous field examples show that after the packer system is set a distinct pressure build-up or fall-off occurs. The non-uniform pretest pressure distribution cannot be neglected in the analysis of the subsequent test events e.g. DST sequence. Significant errors may occur in estimation of the reservoir parameters, in particular the initial pressure.

Second, the use of the constant rate approach in analysing the DST sequence in low permeability formations leads to errors unless the rate sequence, and thus superposition function, is constructed properly. A new method of rate discretisation for the initial discontinuous events (the beginning of the 1st. and 2nd. DST flow period) is presented and the errors resulting from neglecting the true rate sequence are discussed. Field examples present the application of both concepts.

The main objective of this paper is to show that by simple measures it is possible to take account of borehole history and apply rate discretisation to improve the accuracy of interpretation when using standard constant rate analysis software.
Nuclear Tracer Saturation Imaging of Fluid Displacement in Low-Permeability Chalk
Authors: Graue Arne
Published: December 2007

A nuclear tracer imaging technique is evaluated for use in core analysis in studies of oil recovery from chalk reservoirs. In-situ fluid saturation data in long-core flood experiments in chalk, enhance the interpretations of the data; especially in mapping the local recovery efficiencies. In various long core flood displacements, including both drainages and waterfloods, emphasis has been on recording local in-situ saturation development, obtaining recovery efficiencies and studying effects on the saturation profiles from displacement pressure drops, flow rates and initial and final water saturations. The benefits of having access to local in-situ saturation information, the importance of being able to identify rock heterogeneities and tests of repeatability have been stressed.
Reservoir Evaluation and Completion Results From a Horizontal Well in the Mancos B, Douglas Creek Arch, Northwest Colorado
Authors: Middlebrook M. L. , Branagan P. T. , Hill R. E. , Kukal G. C. , Peterson R. E. , McDonald T. S. , Aslakson J. K.
Published: December 2007

The Gas Research Institute (GRI) initiated a data acquisition and analysis project in 1990 with the goal of evaluating the applicability of horizontal well completions In various gas-productive reservoirs. One of the target gas reservoirs in this study was the Mancos Β interval of the Mancos Shale located in the Southwest Rangely Field in northwest Colorado. The overall objectives of the project were to determine reservoir characteristics from a vertical well, model the reservoir, design an appropriate horizontal well completion and compare the production economics of the horizontal well to the economics of the standard vertical well completion.

Data were initially acquired from a vertical well completion in the Mancos Β to evaluate the extent and strike of natural fractures, in-situ stress magnitude and direction, log-derived reservoir characteristics, pre- and post-frac production rates and hydraulic fracture dimensions. A horizontal well was subsequently designed to intersect the interpreted primary set of natural fractures in the Mancos Β. The horizontal well was air-drilled and intersected approximately 1,500 ft of the Mancos Β "main porosity zone."

Borehole image log data indicated that no significant natural fractures were intersected by the horizontal wellbore. A 4-1/2-in. liner was cemented in the well to facilitate hydraulic fracturing after only minimal gas was produced from the open-hole during a 3-week production test. Reservoir modeling and economic forecasting indicated that 2 hydraulic fracture treatments over the 1,500-ft interval would be the most economical. Two fracture treatments were attempted but both resulted in screenouts during the early sand stages. The early screenouts were believed to be directly related to the higher than normal in-situ stresses that were observed during breakdowns and injection tests. Due to the limited vertical extent of natural fractures and the lack of vertical permeability, horizontal well completions in this area of the Mancos Β reservoir do not appear to be a viable completion alternative to hydraulically fractured vertical wells.
NORM Cleaning and Disposal Using Closed-Loop Hydroblasting or Solvent Bath and Underground Injection System
Authors: Lowe D. J.
Published: December 2007

In 1987, BP Exploration (Alaska) Inc. (BPX) began surveying its facilities on the North Slope of Alaska to test for the presence of Naturally Occurring Radioactive Material (NORM). Only one occurrence of NORM in a heat exchanger bundle from a gathering center was found to contain NORM scale at that time. Recent declines in crude oil production from the North Slope oil fields have increased daily quantities of produced water to over 40 million gallons in the Prudhoe Bay Field alone. Regular NORM surveys have continued since 1987 because increases in NORM are generally correlated to increased water production.

In anticipation of a future need for an economical and environmentally sound solution for NORM disposal, BPX and ARCO Alaska, Inc. (ARCO), Co-Operators of the Prudhoe Bay oilfield, began discussions with regulatory agencies and environmental groups to provide a regulatory framework for NORM disposal. The focus of the discussions was to educate both the environmental community and the regulators on the occurrence of NORM, disposal alternatives, and the relative health risks of NORM handling and disposal, compared to other commonly understood health risks faced by our society. This approach created an environment in which rational discussion and decision making prevailed, and ultimately led to approval to dispose of NORM materials either in Class Π wells or in cement slurries to be used in well abandonment procedures. In 1992, BP began disposal of NORM materials via injection after five barrels of the materials were removed from a NORM scale contaminated heat exchanger during cleaning.

This paper discusses the decision making process and the geologic conditions which make NORM disposal via injection the most logical solution for NORM disposal in Northern Alaska. The procedures for NORM removal, processing, and injection are also discussed.
Disposal of Naturally Occurring Radioactive Material From Operations on Federal Leases in the Gulf of Mexico
Authors: Rutherford G. J. , Richardson G. E.
Published: December 2007

This presentation will address the Minerals Management Service (MMS), Gulf of Mexico Outer Continental Shelf (OCS) Region's Letter to Lessees and Operators (LTL) concerning removal and disposal of produced well solids that contain naturally occurring radioactive material (NORM), disposal options for NORM by offshore operators of Federal leases, and data gathered from NORM disposal applications.

Disposal of produced well solids containing NORM from operations on Federal leases in the Gulf of Mexico will continue to be a concern for operators and for the regulating Federal agencies. On December 11, 1991, the MMS's Gulf of Mexico OCS Region sent an LTL concerning removal and disposal of well solids that contain NORM. The LTL provides interim guidelines to monitor closely the disposal of well solids containing NORM and to assist in the collection of data to establish regulations necessary for NORM disposal. The LTL contains disposal criteria and requirements for applications, sampling, testing, and recordkeeping. An operator's disposal options may include encapsulating material in abandoned wells, injecting material into depleted reservoirs, and cleaning material for overboard disposal. Overboard disposal of produced well solids is limited to material that meets National Pollution Discharge Elimination System (NPDES) standards and contains very low levels of NORM, i.e., dose equivalent rates of less than 25 microroentgens per hour above background levels.
Environmental Aspects of Oil and Gas Acquisitions and Divestitures
Authors: Dodson C. J.
Published: December 2007

Environmental issues in the oil and gas exploration and production industry continue to grow and become more complex. As the domestic industry is reshaped through acquisitions and divestitures, the associated environmental issues become a major factor in this evolutionary cycle. An understanding of the environmental aspects of a transaction and the timely and complete management of them will greatly assist in a successful transfer of assets for both the buyer and seller. Early identification of the environmental aspects of the acquisition/divestiture and involvement by the key personnel in their management should prevent those costly surprises from a governmental agency or a court at a later date.
The Use of Geophysical Surveys for Conductive Groundwater Plume Assessment During Remediation
Authors: Dalton M. S.
Published: December 2007

Surface geophysical surveys (electromagnetic) were used to reduce the cost, and increase the effectiveness of the assessment and remediation of a conductive ground water plume in Michigan. Following the release of an estimated 50 bbl. oil and 800 bbl. brine from a pipeline rupture, an inexpensive electromagnetic (EM) geophysical survey was performed to help define the areal extent and configuration of impacted ground water. Test borings, monitor wells, and an interceptor drain system were installed based on the results of the EM survey. Remediation is being accomplished by pumping impacted ground water from the drain and injection of the purged water into a Class IIR secondary recovery injection well.

Throughout remediation, quarterly EM surveys have been used to demonstrate progress. Over the three year remediation period, the chloride concentration in the most contaminated monitor well has been reduced by 99.7%, from 68,000 to 200 milligrams/liter (mg/l). The highest apparent conductivity in the plume has been reduced by 84.5%, from 290 to 45 millimhos/meter (mmho/m).
The Environmentally Sensitive Contract
Authors: Fachin G. M. , Fachin Gary M.
Published: December 2007

An analysis of the application of selected environmental laws and regulations to onshore exploration and production activities and of how such laws and regulations compel new contractual provisions. Aspects of the federal Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), federal Resource Conservation and Recovery Act (RCRA), and California air pollution control program along with judicial interpretations are examined.
Southeast Lost Hills Hydraulic Fracturing Stimulation of the Antelope Shale Zone: Case History
Authors: Martinez A. D. , Marquez M. R. , Shotts K. D.
Published: December 2007

This paper presents a case history of the hydraulic fracturing stimulations applied to the Antelope Shale (AS) zone in the Southeast Lost Hills (SELH) Field located in Lost Hills, CA. Over 100 wells have been stimulated in this low permeability naturally fractured reservoir since 1979. The hydraulic fracture treatments have been refined to their current empirically "optimized" design.

Results are presented concerning production response vs. sand volume placed and the effect of various proppant sizes on production and job success. In addition, results are given from the use of inter-stage pressure bombs hung below bridge plugs for determination of inter-zonal communication during treatments. Also, the paper discusses the developed perforating schemes and their effect on zone coverage, and the identification of reservoir depletion in various infill wells exemplified by lower fracture gradients.
Interference Pressure Behavior in Stratified Reservoirs
Authors: Hatzignatiou D. G. , Ogbe D. O.
Published: December 2007

In this paper semi-analytical solutions for interference testing in a two-layer reservoir are presented. The two layers may or may not be separated by a semi-permeable shale barrier. The solutions are derived assuming that (i) pressure equilibrium existing in the more permeable layer, due to its high vertical permeability, allows only radial flow in this layer, and (ii) the radial flow in the tighter layer is negligible due to the permeability contrast between the two layers. The upper reservoir boundary condition allows the modeling of either a no-flow or a constant pressure upper reservoir boundary which can be used to represent a gas cap. Wellbore storage and skin effects are considered at both active and observation wells. The dimensionless pressure and pressure derivative solutions are obtained for both layers at the observation well and for the producing layer at the active well.

The results obtained indicate that the interference pressure behavior in a stratified reservoir with vertical crossflow taking place from the supporting layer to the producing layer is affected significantly by the transmissibility ratio of the two layers, the properties of the shale barrier separating the two layers, and the skin and wellbore storage at both active and observation wells. It is shown that depending on the magnitude of the wellbore storage at the active and/or observation well, the early time interference pressure behavior may be masked making proper interpretations of early-time pressure transient test data difficult.
Faulting: A Major Control on Fluid Flow and Production Performance, Prudhoe Bay Field, Alaska
Authors: Kay E. A. , Bodnar D. A. , Cazier E. C.
Published: December 2007

During 15 years’ development at Prudhoe Bay, some wells have been drilled near, or inadvertently through, faults, often resulting in impaired well performance. This paper provides examples of fluid movement through and along faults using open and cased hole logs, and production data. Where data exist, faults can be shown to be transmissible where reservoir juxtaposes reservoir. Data from recently drilled wells show pressure communication across major faults. Highly transmissible fault planes allow rapid movement of water or gas to the perforated intervals of production wells. Other problems result from drilling through fault zones including lost circulation, adverse hole conditions causing poor wireline log data and inadequate primary cementing. The majority of wells are unfaulted in the reservoir section, but with continued infill drilling, targeting new wells to avoid faults becomes increasingly difficult. The importance of accurate structural mapping tied to well data, therefore, cannot be overstated.
Determining Wellbore Pressures in Cement Slurry Columns
Authors: Prohaska Michael , Ogbe D. O. , Economides M. J.
Published: December 2007

This work discusses the major factors affecting the pressure drop in the cemented annulus which are filtration from the wellbore into permeable layers, shrinkage of the slurry due to hydration, and changes in the rheological properties of the slurry. A model for determining wellbore pressures in cement slurry columns is presented. It accounts for the depth-dependent or placement history-dependent behavior of the gel strength evolution. Experiments conducted in the laboratory demonstrate that static gel strength development is a function of temperature, pressure and shear rate. Results show that large differences in wellbore pressures can be obtained when the depth-dependent characteristics of gel strength are neglected in wellbore pressure loss calculations.
Simulation Study of Steam-Assisted Gravity Drainage Process in Ugnu Tar Sand Reservoir
Authors: Kamath V. A. , Sinha Sandeep , Hatzignatiou D. G.
Published: December 2007

A two-dimensional numerical model of the steam-assisted gravity drainage process with a pair of horizontal wells (SAGD) is developed for heterogeneous, layered tar sand reservoirs. As a case study, this model is applied to Ugnu reservoir to study the effect of heterogeneity on the growth of steam chamber and the process performance.

A detailed simulation study is conducted to determine the effect of various reservoir parameters such as porosity, permeability, initial mobile water saturation, Dykstra-Parson’s permeability variation, reservoir anisotropy and shale barriers on the SAGD process performance in Ugnu reservoir. Also, the effect of process parameters such as steam injectivity, steam quality, steam temperature, horizontal well length, vertical and lateral well spacing is studied.
Rapid Evaluation of the Impact of Heterogeneity on Miscible Gas Injection
Authors: King M. J. , Blunt M. J. , Mansfield M. M. , Christie M. A.
Published: December 2007

To predict and manage petroleum production there are two challenges: (i) to generate and utilise tremendous detail in our reservoir description (ii) to recognise that the majority of this detail is uncertain. Techniques, therefore, are necessary to assess uncertainty while making predictions of oil, water, and gas production. We demonstrate that by using a mixture of old and new techniques (streamlines and fine grid simulation) that we obtain the speed of the first while retaining the rigor and accuracy of the second. The method is applied to the rapid evaluation of the impact of reservoir heterogeneity on miscible gas injection.
Sensitivity of Oil Recovery to Grid Size and Reservoir Description in Fluvially Dominated Deltaic Facies
Authors: Haajizadeh Masoud , Begg S. H.
Published: December 2007

We address the question of what grid-size is necessary to adequately simulate oil recovery from a variety of heterogeneous facies found within a fluvial-deltaic system. We start by generating geological models of core-plug-scale poro-perm heterogeneities based on a geological understanding of the spatial distribution of lithotypes within a facies. This fine scale distribution is then re-scaled to different reservoir simulation grids which coarsen both horizontally and vertically. The finest simulation grid was such that the effect of re-scaling was negligible and thus the simulation model was almost an exact representation of the "true" reservoir. Equivalent homogeneous models, using the global effective properties of the fine-scale reservoir description, were also run. This enabled us to compare purely numerical effects with the effects of re-scaling the heterogeneous description. Waterflood and gasflood simulations were then run on each grid.

For the heterogeneous systems considered, the coarser grids under-estimated recovery - by up to 16%. Also, for the homogeneous models, waterflood recovery always decreased as the grid coarsened; gasflood recovery was relatively insensitive to block size. Further, recoveries were always higher in the heterogeneous model compared to the homogeneous model at any given grid size.

Finally, recovery and PI were grossly under-estimated at gridblock sizes that were approximately the same as that of significant heterogeneities - finer or coarser grids did a better job. The global effective permeability of the re-scaled grid was much lower for these inadequate grid sizes. Global effective permeability can thus be used to assess grid adequacy with respect to heterogeneity prior to performing simulations.
Use of Coiled Tubing for Abandoning Shallow Thermal Wells, South Belridge Field, Kern County, California
Authors: Fram J. H. , Eberhard M. J.
Published: December 2007

This paper details the use of coiled tubing for spotting cement plugs without a workover rig present, during abandonments of 100 shallow, thermal wells in the South Belridge Field. This method decreased the cost of this portion of the abandonment operation by $2000 per well. The paper describes why multiple well abandonment programs are common in thermal fields. The requirements for effective abandonment in thermal fields are also covered. Workover rig and coiled tubing abandonment methods are discussed and compared. The methodology used for selection of an effective and less expensive thermal abandonment cement slurry is outlined. This paper shows that if operating, service company and regulatory agency personnel work together, the cost of abandoning wells can be substantially decreased without decreasing the effectiveness.
Low-Pressure Gas Injection To Enhance Production in a Pressure-Depleted Reservoir at Elk Hills Oil Field, California
Authors: DeRose W. E. , Ottaviani W. L. , Harris B. R.
Published: December 2007

A low pressure gas injection pilot was implemented in the Shallow Oil Zone Reservoir of the Elk Hills Field (Naval Petroleum Reserve #1 in California) to investigate the technical feasibility and economic viability of injecting gas for pressure assistance.

This paper highlights various aspects of the gas injection project including the use of perfluorocarbon tracer to detect gas movement, the value of geologic sublayer mapping, and the need for a multi-mode monitoring program.

Pilot results are reported in terms relative to initial expectations based on volumetric calculations and reservoir modelling. Furthermore, project objectives and strategies related to reservoir communication and optimum depletion pressure are also reported.

Since the success of this project was predicated on a unique, synergistic working relationship among the principals, a portion of this paper addresses the merits of such a relationship.
Petroleum Engineering Nineties Style: Caroline Major Sour Gas Condensate Project
Authors: Harvey P. A. , Coppes J. L. , Webb R. J. , Lebiadowski G. P.
Published: December 2007

This paper Is an introduction to the sub-surface aspects of the $1 billion Caroline sour gas condensate development. Technical aspects concerning reservoir geology and fluids, well performance and depletion strategy are reviewed.

The Caroline field contains 60 bcm (2.1 tcf) of liquid-rich gas containing 35% H2S. Production is from the high deliverability Swan Hills reservoir at a depth of 3800 m (12400 ft). The nature of the reserves and their proximity to rural population centers impacts the planning process.

The theme of the paper is that hydrocarbon development planning in the 1990's and beyond is constrained due to the legitimate concerns of the local and broader public. In the Caroline example, there was minimal well testing prior to start up as a result of these concerns. Still, a strong consultative effort resulted in an effective use of the data for planning purposes. These efforts determined an appropriate scope for the project which was started up on time and on budget. With limited production data available up front, Caroline is not unlike a major offshore project. The challenge for marketers, builders, operators and sub-surface technical specialists was to provide and execute a development plan and depletion strategy for the project that would meet the needs of both the owners and the affected parties.
A Tight Gas Field Study: Carthage (Cotton Valley) Field
Authors: McCain W. D. , Voneiff G. W. , Hunt E. R. , Semmelbeck M. E.
Published: December 2007

INTRODUCTION

Evaluation of the need for infill drilling in complex, low-permeability, gas reservoirs requires the application of advanced technology. Use of typical engineering tools such as conventional decline curve analysis, conventional pressure transient analysis, and single layer reservoir descriptions often create inaccurate results and misleading conclusions. Despite the accuracy of advanced analysis techniques, these techniques are typically not performed on a well-by-well basis in field-wide studies because the cost cannot be justified. As a result, accurate conclusions, valid for all areas of a field, are not obtained.

In this paper we present a practical means of applying advanced analysis techniques to an entire field. We describe a powerful statistical method for dividing the reservoir into areas of like productive behavior. This method provides an unbiased means of comparing well performance, selecting areas for advanced analysis, and defining the areal locations where specific conclusions apply. Emphasis is placed on incorporating a sound geological and petrophysical description, and evaluating the consistency of reservoir descriptions developed through independent geological and reservoir engineering techniques.

This analysis technique was used to evaluate the infill drilling potential of the Carthage (Cotton Valley) field in east Texas. The Carthage field, discovered in 1968, is a thick, layered, low-permeability gas reservoir underlying 250,000 acres in Panola County, Texas. See Fig. 1. At the time of this study, there were approximately 900 wells producing 400 million cubic feet and 300 barrels of condensate per day. The Carthage Cotton Valley sand has been classified as "tight gas" by the FERC. Prior to this study, there were three periods of intense drilling activity corresponding to authorizations of 640-, 320-, and 160-acre drilling densities. Carthage is currently experiencing a fourth active drilling period, in which numerous wells are being drilled on 80-acre spacing in selected areas of the field.
An Integrated Team Approach for Improving Company-Wide Stimulation Design and Quality Control
Authors: Nagel N. B. , Arnold W. T. , McCoy M. W. , Scott S. L. , Thrasher T. S.
Published: December 2007

In 1987, Phillips Petroleum Company identified well stimulation as an area where costs were high and efficiency could be improved. Efforts to improve performance were addressed by creation of the Formation Completion Task Force. This task force has undertaken a variety of training and technology transfer tasks and, most importantly, has served as a vehicle for change. The inter-office teamwork fostered by the task force has allowed rapid implementation of new technologies throughout the company. Specific case histories are given which show the impact that these changes have had on improving well production as compared to previous stimulation efforts. The tangible results of these efforts have been an acceleration of production and an increase in reserves, which have been realized through a doubling of average sand concentrations pumped, company-wide implementation of the forced closure concept, and intense, on-site quality control of fracture treatments. Since 1989, the impact of these measures on world-wide operations is estimated to be well over 150 million dollars in accelerated cash flow and added reserves.
The Integrated Team Approach to the Optimization of a Mature Gas Field
Authors: Hooi H. R. , Goobie Lorraine , Cook Robert , Choi Joseph
Published: December 2007

From 1988 to 1991 an integrated surface and subsurface simulator was designed and constructed to assist the petroleum engineer in the development and management of gas fields. The developed Gas Field Planning Tool, GFPT, allows the user to define the business environment strategies of a field since it has not been customized for any particular field.

This paper briefly describes the GFPT functionality and the application of the simulator in the study of several development scenarios for a maturing gas field in a multi-disciplinary team enviroment.