bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring Sustainable Economic Development Indicators with Fuzzy Sets: The Sustainable Development Index
Authors: Agbon I. S.
Published: December 2007

Sustainable economic development means different things to different stakeholders. It encompasses economic, social, political and environmental issues. Therefore, it is very difficult to measure and monitor. There has been marginal success in developing indicators that capture sustainable economic development from the perspective of the host community.

This paper develops a Sustainable Development Index (SDI) that captures the social, economic, political and environmental impact of oil and gas activities on the host community. Using a fuzzy logic model, fuzzified host community dimension indices are developed for indicators such as Life, Education, Economics, Environment, Political Participation, Social Participation (access to jobs, water, electricity, telephones, internet etc), and Gender Equality. The fuzzified outputs are then aggregated and defuzzified into a Sustainable Development Index for the host community. Using the above method, the annual SDI of a host community can be measured over the project lifetime. For a given year, the SDI of different host communities can also be measured and compared.

The paper concludes that a Sustainable Development Impact Assessment (SDIA) study should be carried out before beginning any oil and gas project. This study should be done in addition to the Environmental Impact Assessment (EIA) study. The SDIA study would establish a baseline SDI for the host community and enable oil and gas companies to monitor the sustainable economic development of the host community during the project lifetime. Oil and gas projects that do not increase the SDI of the host community during their life cycle should be rejected.
Acid Fracturing of Power Water Injectors: A New Field Application Using Polymer-free Fluids
Authors: Al-Muhareb Mohamed A. , Nasr-El-Din Hisham A. , Samuel Elsamma , Marcinew Richard P. , Samuel Mathew
Published: December 2007

Seawater injection has been used to maintain the reservoir pressure in a carbonate reservoir in Saudi Arabia. However, the injectivity of some vertical wells in this field is limited due to low reservoir permeability (less than 20 md). Conventional matrix acid treatments did improve the injectivity to varying degree. However, to achieve the required injection rate, some of water injectors need to be stimulated by acid fracturing.

Various acid systems have been evaluated to acid fracture injection wells. A thorough literature survey and lab testing eliminated acid systems that utilize acid-soluble polymers (both linear and cross-linked). This is mainly due to the formation damage associated with polymers, and also these systems required back-flow of the treated wells for cleanup.

To eliminate formation damage due to polymers, flowback for cleanup, and to enhance well performance, a polymer-free viscoelastic surfactant fluid was utilized in acid fracturing treatments. The fluid system includes the non-damaging viscous pad and polymer-free leak-off controlled acids. The treatment was successfully applied in the field. Cleanup by flow back was eliminated with resulting in significant increases in well injectivity comparable to horizontal wells drilled in the same area.
Effective Stimulation of Multilateral Completions in the James Lime Formation Achieved by Controlled Individual Placement of Numerous Hydraulic Fractures
Authors: Surjaatmadja Jim B. , McDaniel B. W. , Clint Brian , East Loyd E. , Schoolfield Clint , Herbel Stephen R.
Published: December 2007

Fracture stimulation of long openhole horizontal wells is known to be extremely difficult when conventional stimulation methods are used. The level of difficulty increases significantly when multiple fractures are to be placed in openhole multilateral wells. A relatively new hydrajetfracturing process may be one of only a few methods that can be used to fracture-stimulate multilateral wells effectively without the use of sealing devices. This process is unique because many fractures can be placed at precise locations as desired. After reviewing the recent effectiveness of the process in single-wellbore openhole completions, an operating company elected to evaluate this stimulation method for multilateral wells.

This paper describes implementation of this new technology in three multilateral wells drilled through the James Lime formation in the east Texas/west Louisiana area. Past experiences of fracture acidizing James Lime wells with hydrochloric acid (HCl) indicate that this process can be successful as a stimulation process. However, the effectiveness of fracturing these types of wells with sand or proppants was not proven. The three wells were treated using three fracture-stimulation approaches: (1) multistage combining two stages each of HCl acid and proppantfracturing stimulation, (2) multistage with only a single acid stage, and (3) proppant-fracturing stimulation alone. Well production responses resulting from these three approaches are evaluated in this paper.
New Environmentally Friendly Surfactant Enhances Well Cleanup
Authors: Hinkel Jerald J. , Brown J. Ernest , Gadiyar Bala R. , Beyer Eric
Published: December 2007

Saturation changes resulting from leakoff during stimulation treatments reduce the relative permeability to hydrocarbons in the invaded zone. Historically, surfactants have been added to stimulation fluids to lower the surface tension of the fluid in order to facilitate cleanup and mitigate formation damage caused by the filtrate, and this approach has become dogma. This paper, while recognizing the importance of low surface tension, focuses primarily on enhancing cleanup by altering wettability. Few studies have been performed to investigate the impact on cleanup resulting from use of surfactants to change formation wettability.

A rapid screening test has been devised to measure the effect that various additives, when added to aqueous fluids, will have on a synthetic core. The effect is determined by measuring the rate at which the fluid, with and without additives, is imbibed into a synthetic core. This rapid screening test has proven to be quite effective, in that it is simple, quick, inexpensive, and, above all, accurate. A further advantage of this method is that it provides a simple method to estimate contact angles and, therefore, provides a good measure of wettability. The simple imbibition test method has been validated by comparing the results from these tests with the results from sophisticated coreflow experiments. Results were further confirmed by greater than 40 successful treatments in the field.

In addition to cleanup performance, the research presented here focused on the environmental impact of the stimulation fluid. The ultimate outcome of the project was a stimulation fluid that performs in a superior fashion while meeting US Environmental Protection Agency (EPA) environmental requirements for offshore discharge in the Gulf of Mexico.
New Findings on Damage Potential, Geochemical Reaction Mechanisms, and Production Enhancement Applications for Citric Acid
Authors: Al-Khaldi M. H. , Nasr-El-Din H. A. , Blauch M. E. , Funkhouser G. P.
Published: December 2007

Application of citric acid for damage removal in both clastic and carbonate rocks has historically not received widespread acceptance due to formation damage concerns regarding precipitation of calcium citrate. In addition, usage of citric acid in place of hydrochloric acid has been avoided due to lower bulk carbonate dissolving power relative to hydrochloric acid. However, environmental, safety, and corrosion concerns with using hydrochloric acid have sparked renewed interest in citric acid for stimulation.

This paper reconsiders the use of citric acid as both an additive to conventional hydrochloric acid systems and as a stand-alone acidizing fluid. The paper reviews extensive laboratory work focused on understanding reaction pathways and geochemical precipitation issues, and takes a new look at paradigms related to the calcium citrate issue.

Laboratory studies performed independently by two research laboratories address two main areas of investigation: (1) Evaluation of potential geochemical reaction paths and precipitation of calcium citrate and (2) mechanisms for generation of differential etching in two carbonate rock lithotypes. The described mechanism for etching enhances conductivity in a contrasting mode compared to hydrochloric acid.

Findings based on this work provide new insights into the applications, usage and potential limitations of citric acid. A newly proposed process for downhole reaction is presented. This process differs greatly from long-held paradigms built on a foundation of bench-top experimentation. Factors controlling downhole reactions are disclosed and the results of core testing and fracture conductivity are presented.
A New Comprehensive Hydraulic Fracturing Technology to Minimize Formation Damage in Low Permeability Reservoirs
Authors: Jiang Tingxue , Wang Xugang , Shan Wenwen , Wang Yongli
Published: December 2007

In low permeability reservoirs, hydraulic fracturing treatments are usually utilized to evaluate reserve quality in exploration wells or make producing wells economically. As we all know that the formation damage during a hydraulic fracturing job may reduce a well's production rate in a large degree, so, a new comprehensive hydraulic fracturing technology aiming to minimize formation damage is put forward in the paper. Compared with the past common hydraulic fracturing technology, it mainly contains 7 sections:1)the optimization of PAD volume;2)the optimization of polymer concentration used in fracturing fluid;3)the technology of high sand concentration and the optimized proppant pumping schedule(more than 10 stages) correspondingly;4)the optimization of pumping rate and increasing pumping rate step by step during last stages of proppant pumping;5)fracturing fluid additives selection and the optimization of breaker schedule;6)forced closure technique is performed at the moment of shut-in;7)the control of bottomhole flowing pressure during flow back of fracturing fluid and production stage in the case of stress sensitivity which is usually a main characteristic of low permeability reservoirs. After the study, four exploration wells belonged to a certain oil field of petrochina are hydraulically fractured using above technology system. The well A1 and A2 get an idea post-fracturing rate of 9.12m3/d and 11.44m3/d respectively, compared with 1.94 m3/d of their adjacent well A7. what's more, a new geology reserve has been determined up to 5,000,000 tons as a result of above 2 successfully fracturing treatment wells. Similarly, the well A5 get a rate of 16.82 m3/d compared with 0.78 m3/d of its adjacent well A6, and the well A3 get 30.57 m3/d compared with 25.7 m3/d of its adjacent well A4. Overall, the comprehensive hydraulic fracturing technology put forward in the paper has a great significance in evaluating reserve quality, sometimes it may even be used to find an undiscovered reserve. On the other hand, it may also increase economic benefit of a producing well in low permeability reservoirs.
Media Sizing for Premium Sand Screens: Dutch Twill Weaves
Authors: Ballard Tracey , Beare Steve
Published: December 2007

Dutch twill weaves are a common filter medium for premium and expandable screens. This paper attempts to address the question of which weave aperture size to select for a particular sand. An extensive matrix of sand retention tests using reservoir sands has been performed to gain a better understanding of the retention and plugging performance of dutch twill weaves. Several weaves have been used with different weave aperture sizes as measured by a glass bead test. Sand retention testing is often fraught with experimental artifacts and the results are very dependent on experimental conditions. However, the general trend in the data from a number of tests shows good correlation between some aspects of the sand distribution and the retention performance. In particular the diameter of the largest sand grains for a particular sand (d1, d5 and d10) are shown to be important in determining retention performance. From this data, an aperture sizing criteria for dutch twill weave sand screens is proposed. The plugging performance of the weaves is also examined with respect to weave open area and sand uniformity.
Assessment of Total Skin Factor in Perforated Wells
Authors: Yildiz Turhan
Published: December 2007

In this study, we present methods to predict the total skin factor for perforated and damaged wells correctly. The non- linear interaction between individual skin components is accurately represented in the methods. We show that the total skin factor models based on the simple addition of individual skin factors due to formation damage, perforation, inclination, partial penetration etc… do not work.
Formation Damage Laboratory Testing - A Discussion of Key Parameters, Pitfalls and Potential
Authors: Byrne Michael , Patey Ian
Published: December 2007

Formation Damage Laboratory Testing is routinely performed to select optimum drilling, completion and other fluids prior to their deployment in wells. Major decisions which impact the productivity or injectivity of wells and fields are often based on laboratory tests. This paper aims to resolve some of the arguments and diversity in the procedures for laboratory formation damage tests and present clear evidence to support opinions expressed on the merits of particular tests. The paper is deliberately non-reservoir specific and will formalise in one document evidence, opinions and suggested test improvements.
New Mechanisms of Formation Damage: Lab Studies and Case Histories
Authors: Nasr-El-Din H. A.
Published: December 2007

Formation damage occurs during the lifetime of many wells. Loss of well performance due to formation damage has been the subject of several review articles. Fines migration, water, emulsion blockage, inorganic scale, asphaltene, and other organic deposition are a few mechanisms that can cause formation damage.

The present paper discusses new formation damage mechanis ms that are caused by various chemical treatments. These include: adsorption-type scale squeeze treatments (phosphonate-based inhibitor), solvent treatments (a neat mutual solvent) to remove water blockage in a tight carbonate reservoir, and regular mud acid (HCl:HF at 12:3 weight ratio) to remove drilling mud filter cake in sandstone reservoirs. These treatments were designed to remove a known form of formation damage. However, they created new forms of formation damage, which resulted in a significant decline in the performances of several wells.

Case studies of new damaging mechanisms that resulted from various chemical treatments are discussed in this paper. Details of lab and fieldwork that were performed to identify the damaging mechanisms and determine its impact on well performance were addressed. Finally, the paper highlights the remedial actions and field application that resulted in restoring the performance of various wells without affecting the integrity of the formation.
Reversible Invert Emulsion System used to Significantly Increase Water Injection Rates in an Open Hole, Stand-Alone Screen Completion in West Africa
Authors: Dick M. A. , Svoboda C. , Jones M.
Published: December 2007

Increasing water injection rate at low injection pressures with low cost has always been a goal of any reservoir pressure maintenance program. During the development of an offshore West Africa field, the operator has discovered a method to significantly increase water injection rate at low injection pressures.

This paper describes the utilization of a number of new technologies to drill and complete a 2,109-foot section. The well was drilled in a geologically challenging reservoir containing inter-bedded shales. The project was planned with geological, drilling/completion and injectivity goals in mind. The high-rate water injector was completed open hole with a stand-alone screen. A number of new technologies were used during the drilling and completion phase of this well includes: Specially designed reversible invert emulsion reservoir drill-in fluidUtilization of a completion screen flow through testUnique displacement sequenceSpecially designed organic acid cleanup treatment

Compared to best offset drilled with a low-solids, conventional oil-based mud this operation resulted in a 280 % increase in the water injection rate with a 50% decrease in injection pressure.
Assessing Profitability of Well Interventions on Mature Fields: Well Intervention Profitability Evaluation Method, case study from Cameroon
Authors: Buffet Michael , Mastin Eric , Maguerez Michel , Amiell Patrick
Published: December 2007

The Well Intervention Profitability Evaluation Project was aimed at applying a BP Corporate methodology (WETS, Wellwork Evaluation Tracking System, SPE 30649) to TotalFinaElf's Mature Fields.

When Oil Fields become "mature", drilling new wells may not necessarily be the appropriate solution to grab additional barrels and counterbalance the natural production decline. Progressively, TotalFinaElf Subsidiaries implement well intervention programs designed to recover or boost productivity. A wide range of such interventions is investigated and usually end up performing "spot" operations (a fracturation job, an acid job, a water shut-off …).

Often, when spot interventions prove successful, the idea comes to generalize these proven solutions and perform such interventions more systematically (campaigns). In terms of investments, although costs usually stay much lower than drilling costs, the financial impact may still be significant in subsidiaries where profitability can be "borderline".

Therefore, assessing the real financial impact / profitability of these campaigns needs more than "basic" return on investment calculations.

In one sentence, the method is aimed at Assessing the Profitability (over the time) of a given Wellwork Intervention (fracturations, acidifications, workovers, etc…). By plotting "Cost versus Net Present Value (NPV)", one can draw "scorpion" plots gathering, in an ordered way (decreasing NPV/Investment), all interventions perfomed on corresponding wells. A comparison "Campain X versus Campain Y, Z,…" can also be performed.

Then, the method, applied to an intervention campaign, is a 4 step process: –Evaluate the oil gain over a significant period of time as precisely as possible using an oil field management production data base. An adjusted cost per well is also computed at this stage,–Build and run a "light" economical model, taking into account the production contract and fiscal particularities, and this for each well,–Draw the "scorpion" plots (different durations can be considered) and highlight significant wells plus particular cases on each campaign. Draw conclusions,–Plot different campaigns (if applicable) on the same chart (cumulative NPV versus cumulative cost). Draw conclusions on relative profitability.

This paper comes back first on the methodology followed, then presents the case study of Cameroon which helped calibrating and assessing the interest of the method. Conclusions on the profitability of stimulations campaigns in Cameroon were straightforward and improvement tracks could also be highlighted thanks to this method.
Relative Permeabilities in Co-Current Three-Phase Displacements With Gravity
Authors: Juanes Ruben , Patzek Tad W.
Published: December 2007

We study the character of the equations in the traditional formulation of one-dimensional immiscible three-phase flow with gravity, in the limit of negligible capillarity. We extend our previous analysis, presented in SPE 77539, to incorporate the effects of gravity. We restrict our analysis to co-current flow required for a displacement process; in cases of mixed co-current and counter-current flow, capillarity effects cannot be dropped from the formulation. The model makes use of the classical multiphase extension of Darcy’s equation. It is well known that, if relative permeabilities are taken as fixed functions of saturations, the model yields regions in the saturation space where the system of equations is locally elliptic. We regard elliptic behavior as a nonphysical artifact of an incomplete formulation. We derive conditions on the relative permeabilities so that the system of governing equations is strictly hyperbolic. The key point is to acknowledge that a Darcy-type formulation is insufficient to capture all the physics of three-phase flow and that, consequently, the relative permeabilities are junctionals that depend on the fluid viscosity ratio and the gravity number. The derived conditions are consistent with the type of displacements that take place in porous media. By means of an illustrative example, we show how elliptic behavior can be removed, even when using simplistic relative permeability models.
Identification of Contaminanted Data in Hydraulic Fracturing Databases: Application to the Codell Formation in the DJ Basin
Authors: Popa Andrei S. , Mohaghegh Shahab D. , Gaskari Razi , Ameri Samuel
Published: December 2007

With the advance of computer technologies, digitized data is becoming increasingly available. Currently, many companies are in possession of oil or gas-field databases that contain large amounts of information related to hydraulic fracturing, reservoir characterization, production, drilling, etc. However, not all the records are completely accurate or reflect reality. Errors in stored data can be subjective or objective and can be the result of improper or incomplete data collection, errors in data entry, lack of proper interpretation and others. These errors can later lead to poor, erroneous, or even impossible interpretation of the data. This leads to the question: how much of the data is reliable and how can the contaminated data be identified?

The paper presents a new methodology for identification of contaminated data in hydraulic fracturing databases. The methodology combines a set of artificial intelligence tools, which integrates clustering techniques, neural networks modeling and an iterative process to achieve its convergence goal. The result can be seen as a separation of data into three categories: good data, slightly contaminated data, and "bad" data.

This new methodology is applied to two database cases. In the first case, random records in a sample database were intentionally corrupted. Then, using the new methodology presented in this paper, these records were identified as being contaminated. The second case involves a real situation in a Patina Oil and Gas Corporation hydraulic fracturing database, where using classic approaches, the data was unusable for any artificial intelligence processes. After applying this methodology to identify contaminated data, successful fracturing interpretation was performed.
A Novel Expert System for Multilateral Well Completion
Authors: Garrouch Ali A. , Lababidi Haitham M. S. , Ebrahim Abdullah
Published: December 2007

In this study, we assembled and put under scruitiny variables that affect the drilling and completion of multilateral and horizontal wells. We then formulated reservoir candidate screening criteria for applying multilateral technology, and implemented these criteria in an expert system for designing optimal multilateral well configuration and completion using the leading edge technologies of simple and complex multilateral junctions. The system features the use of fuzzy logic for handling ambiguous completion scenarios.

The main benefits of horizontal wells consist of lowering the development and lifting costs per barrel of oil produced. Multilateral technology multiplies these benefits by adding more reservoir exposure per well, and more exposure per drilling and completion dollar spent. The recent evolution of multilateral technology introduced a large variation of completion options for multilateral wells. Many of these options are simple and basic while others are complex. The development of this fuzzy expert system allows the use of multilaterals in a much wider range of well scenarios, and allows to account for a large number of production-styles constraints and rock-properties conditions.
Integrated Interpretation of Pressure Transient and Injection Profile for an Undulating Dual-Lateral Well
Authors: Ouyang Liang-Biao , Kikani Jitendra
Published: December 2007

Integrated evaluation of bottomhole pressure (BHP) and Water Flow Log (WFL) data from an undulating dual-lateral well provided significant insights into the contribution, flow performance and injectivity of the well. This allowed the setting of long-term performance characteristics for the well design in a multi-layered reservoir.

The injectivity test data (BHP pressure and injection profile) acquired in the first lateral and the DST data acquired in the second lateral were analyzed using a multi-lateral well modeling package designed for a multi-layered reservoir.

Useful and consistent interpretation not only increased confidence but has assisted in making sound reservoir management decisions. Major observations include: The average vertical to horizontal permeability ratio, (kv/kh), a difficult parameter to compute, in general, was determined with an excellent match spanning ten injection and two falloff periods in one lateral and four drawdowns and two buildups in the other.Injection profiles at two different water injection rates were predicted and compared with results based on RST/WFL log. Excellent agreement was achieved. It is demonstrated that the agreement could be further improved if a non-constant correction factor was used in interpreting RST/WFL log data.Well productivity and injectivity indices are dependent upon production/injection time and history. For both the well laterals, the late-time productivity/injectivity index equals to around 11 STB/d/psi.
Successful Horizontal Producers in Midway-Sunset Thermal Operations
Authors: McKay Charles , Jones Jeff , Pomerene Joel
Published: December 2007

Berry Petroleum Company (Berry) has been involved in thermal recovery operations in the Midway-Sunset Field since the inception of the process. The majority of Berry's properties are under cyclic stimulation and several are quite mature. Cyclic steaming combined with high (60°) structural dip present in the Monarch Formation has proven to be a very efficient recovery mechanism to date. Over the past five years Berry Petroleum Company has successfully applied horizontal drilling technology to significantly improve production efficiency in its South Midway-Sunset operation.

Since 1996 over 50 medium-radius horizontal producing wells have been drilled in the Monarch Formation in South Midway. By being drilled generally in the dip direction with a basal lateral placement, these horizontal wellbores expose all of the Monarch sand section to production and provide a means to produce the lowermost oil-bearing strata economically. Vertical well development alone would leave wedges of reservoir unprocessed due to the steep dip of the formation.

This paper will discuss the design, drilling and operational considerations as well as the performance of these horizontal producers. Comparisons of the performance of wells located in areas of differing thermal maturity will be made as well as comparisons to typical vertical wells in each area.
Cement Evaluation Under Extreme Conditions
Authors: Morris Charles , Garcia Chris , Wydrinski Ray , Tinker Steven J. , Mullen Mike , Collins Andrew
Published: December 2007

The completions of ultra-deepwater wells in the Gulf of Mexico are requiring higher mud weights and heavier casing strings in order to economically maximize production rates and to control high-pressure reservoirs. Many operators are completing multiple wells using synthetic oil-based mud weights in excess of 15 lbm/gal, casing with a wall thickness of more than 0.625 in. and special cement materials. Standard cement bond logging tools, however, may not be well suited to evaluate the extreme casing conditions or analyze the casing/cement interface because of the acoustic properties of these materials.

In order to obtain quality answers to the casing/cement evaluation questions, a study was performed to evaluate the results provided by sonic and ultrasonic tools in the different casing materials. The results were obtained from a combination of special small-scale experiments and field applications. This work provides the technical background for extending the ultrasonic measurements beyond normal industry conditions. The measurement resolution and limitations in these extreme conditions are also discussed. It was found that the latest generation of ultrasonic cement evaluation tools could provide high-quality measurements of the casing dimensions and the cement acoustic impedance properties when utilizing the proposed procedures. Field examples are presented to illustrate the actual application and the response of the ultrasonic tools to various extreme cement evaluation conditions.
Decommissioning of Belmont Island, an Offshore Oil Platform
Authors: Ahuja Madhu P. , McGufee J. Cris , Poulter Simon A.
Published: December 2007

Belmont Island was a man-made oil drilling and production island located approximately 8,100 feet offshore of the City of Seal Beach, California in about 42 feet of water. The island was located on State Oil and Gas Lease PRC 186, which contained approximately 1,225 acres of tide and submerged lands located within the Belmont Offshore Field in Orange County, California. During the 40-year active life of the Island, the wells produced approximately 28 million barrels of oil and 24 million cubic feet of natural gas. The State received over $40 million revenue and the operations grossed over $240 million. ExxonMobil terminated oil and gas production in 1994 due to declining production rates.

This fixture in the waters off Seal Beach, survived nearly fifty years as the State’s first offshore oil production facility, Belmont Island became the first man-made oil production island removed from the ocean waters off the California shoreline. After a nearly five year permitting process, the physical removal required 21 months, and was completed in January 2002 with no reportable accidents and no environmental incidents. All of the Island’s components were completely removed except for components buried below the natural seafloor.

The Belmont Island project provides a snapshot of the key issues and technical challenges facing decommissioning projects in today’s regulatory climate. Such challenges included the handling of hydrocarbon contaminated materials in the caisson core, cutting and removal of lead painted concrete and steel surfaces, and the logistical challenges of handling island materials on a gradually smaller work surface. This paper will provide an overview of these challenges and the approaches developed by the project team to address these challenges.
Light-Oil Steamdrive in Fractured Low-Permeability Reservoirs
Authors: Hoffman B. Todd , Kovscek Anthony R.
Published: December 2007

Steam injection into heavy oils has been well characterized over the last 40 years, and while steam has been injected into light oils almost as long, the mechanisms and effectiveness of this process are much less understood. When this lack of understanding is coupled with the complexities of flow in low permeability fractured reservoirs, even less is known. This study examines thermal recovery in low permeability, fractured reservoirs using thermal compositional simulation. A diatomaceous reservoir provided input for the rock model. The oil phase is represented by three pseudo-components that characterize a relatively light crude oil. Both the areal and vertical recovery efficiencies are improved for steam injection compared to water injection. The incremental recovery depends on the distribution of permeability and is greatest for homogeneous distributions.

In regard to recovery mechanisms, thermal expansion of the hydrocarbon fluids accounts for over half of the incremental recovery early in the steam drive; after roughly 0.4 pore volume of steam injection (cold water basis), the incremental recovery is split equally among thermal expansion, vaporization, and oil viscosity reduction. Late time behavior is dominated by vaporization as the distillate bank breaks through to the producer. As a consequence of steam injection three separate fluid banks form: a cold water bank, a combined hot water and distillate bank, and the steam front. Hence, displacement mechanisms are substantially different from the heavy-oil situation where oil viscosity reduction and, frequently, gravity drainage are dominant. Although the study uses a diatomite rock and fluid model, this work clearly extends to include all low permeability fractured reservoirs that have low primary and waterflood recoveries. For such reservoirs, significant additional recovery is obtained by implementing a steam drive.
Fault Identification and Modeling for Production Enhancement
Authors: Yang An-Ping , Eacmen J. C.
Published: December 2007

The Kern River Field has been under steam flood thermal recovery for many years. Faults with even small throw can significantly affect the flow of steam and flow of heated oil. By identifying the spatial distribution of faults, steam injection, perforation, an infill well can be better planned to recover more oil at lower cost.

Seismic data are unavailable for the Kern River Field. Fault identification is based on well data. There are three main approaches in fault identification with well data: Areal analysis of sand and horizon correlation or production anomaly. This helps identify areas where there may be faults.Well pair sand correlation dip variation along depth. A change in apparent dip may indicate fault intercepting with a well.Well pair visual correlation. This is a common method used for well correlation and fault identification

A systematic procedure has been developed to integrate the three approaches. Fault interceptions at different wells are modeled into fault surfaces with consistency checking of fault dip and throw variation along the fault. Fault throws as small as 5 to 10 ft can be identified and modeled.

With a three-dimensional model of the faults, three-dimensional distribution of sand, temperature, and remaining oil saturation can be modeled to the correct positions.
Role of Small-scale Variations in Water Saturation in Optimization of Steam Flood Heavy Oil Recovery in the Midway-Sunset Field, California
Authors: Schamel Steven , Deo Milind
Published: December 2007

In recovery of heavy oil by steam flood’ efficiencies can be realized by limiting the placement of steam to portions of the reservoir with highest oil saturations, thus reducing the disproportionate loss of heat to connate water. This optimization strategy requires knowledge of water saturation (Sw) distributions within the heavy oil reservoir at the scale of operations. Application of this strategy has contributed to the successful reactivation of the shut-in Pru Fee property in the Midway-Sunset field one mile west of Taft, a DOE Class 3 oil technology demonstration project.

The 40 new wells drilled and logged within the 40 acre Pre Fee property together with a single continuous core have permitted 3D mapping of Sw within the 250–350 ft thick pay zone in the Monarch Sand reservoir. Water saturations are observed to vary at three different scales: A systematic vertical reduction in Sw through a 100–150 ft interval above the OWC due to dominate capillary influence where the buoyancy effects are diminished by the low density contrast of the 13º API oil and formation water.Lateral variations in Sw on the scale of 10–100 ft due principally to prior oil production from the reservoir, but modified by its internal stratigraphic architecture.Bed-to-bed variations in Sw on the order of a few feet or less constrained by grain-size controlled differences in porosity-permeability in these crudely graded sands.

Overall production efficiency in steam flood has been improved by limiting steam injection to the upper one-half to two-thirds of the pay zone, where Sw is lowest. Knowledge of the lateral variations in Sw has permitted more accurate appraisal of the effectiveness of individual producers and nine-spot injector-producer arrays. The recognition of the bed-to-bed variations has permitted a better petrophysical model for calibrating Sw calculated from logs.
Rose Field: Surface Tilt Mapping Shows Complex Fracture Growth in 2500’ Laterals Completed with Uncemented Liners
Authors: Minner W. A. , Du J. , Ganong B. L. , Lackey C. B. , Demetrius S. L. , Wright C. A.
Published: December 2007

The Rose field in central California produces oil from the McLure shale, a low permeability overpressured quartz-phase siliceous shale interval at 8000’ depth. The field has been developed with horizontal wells, completed with an uncemented liner and a single hydraulic fracture treatment to cover the average 2500’ lateral length. Based on initial vertical well experience in the adjoining North Shafter field, this horizontal well strategy greatly improves the ability to place hydraulic fracture treatments, and improves well economics by accessing a greater volume of reservoir rock per well. However, the half-mile long completion interval and the uncemented liner unavoidably add uncertainty to fracture treatment distribution along the lateral. Using limited entry perforation strategy, does the completion technique effectively stimulate the entire target lateral interval? To assist with answering this question, the fracture diagnostic of surface tiltmeter fracture mapping was used to evaluate fracture growth during the nine fracture treatments. Tilt results include fracture orientation and the approximate location and volume distribution of fracture components along the lateral.

The original intention of the uncemented liner strategy in the McLure shale was to align the wellbore with the preferred fracture orientation, thus resulting in the initiation and propagation of a simple longitudinal fracture along the entire lateral. However, the actual fracture growth pattern was found to be much more complex, with vertical fracture components in two orthogonal directions, and a significant horizontal fracture component. Considering overall averages, about 45% of fracture volume was contained in transverse fracture components (~N60°W), while 35% of fracture volume was in longitudinal components (~N30°E), and the remainder in horizontal fractures. This complex multiple-component fracture growth is believed to be due to a small in-situ stress bias, combined with the impact of the completion technique and the naturally fractured character of the McLure shale.

Fracture orientation and approximate component distribution along the lateral are compared and discussed for the nine treatments evaluated. Although the uncemented liner technique did not achieve the original intent of longitudinal fracture dominance, reasonable lateral coverage was achieved. Based on 1-year cumulative production, the limited dataset is suggestive, but not conclusive, that horizontal and transverse fracture growth is preferable to longitudinal fracture growth.
Prediction of Rock Mechanical Properties from Wireline Data and their Use in Drilling Simulation
Authors: Cooper George A. , Hatherly Peter
Published: December 2007

We have used wireline log data to derive rock strength and abrasivity as a function of depth for a well. This information was fed to a computer-based drilling simulator that was then used to drill the well in simulation using the same operating parameters as had been used in the field.

Comparison of the field and simulated rates of penetration and states of wear of the bit for different bit runs showed close agreement. This demonstrated not only that our technique for deriving the rock-mechanical strength and abrasivity values from the geophysical data was correct, but also that the drilling mechanics algorithm in the simulator was able to match the drilling performance in the field.

We believe that when the simulator is tuned in this way to reproduce field drilling behavior, it may be used to investigate different drilling scenarios with the objective of finding the most desirable conditions for drilling a future well in a similar geological environment.
Physics-based Reconstruction of Sedimentary Rocks
Authors: Jin Guodong , Patzek Tad W. , Silin Dmitry B.
Published: December 2007

We develop a depositional model that reconstructs numerically the geometrical structure and mechanical properties of natural sedimentary rocks in two and three dimensions. Our emphasis is on unconsolidated sands and sandstones. Our model has the following distinctive features: (1) it accounts for the dynamic geologic processes of grain sedimentation and compaction, and the diagenetic rock transformations; and (2) it reproduces the mechanical rock properties. The main input parameters are the grain size distribution, the final rock porosity, the type and amount of cement and clay minerals, the coefficient of friction, the bond strength parameters, and the grain stiffness moduli. The initial grain shapes are circular in 2D and spherical in 3D. Our depositional model can also be used to study the initiation, growth, and coalescence of micro-cracks in the rock. The proposed approach makes it possible to model the accumulation of rock damage and fracture propagation. The development of micro-cracks in, for example, a 2D marble rock model is studied under increasing vertical stress. Both the box fractal dimension of the micro-crack distribution and its variation with the applied stress are estimated.
Developing and Using Slimhole Rotary Steerable Systems in the North Sea Changing the Economics of Mature Asset Drilling
Authors: Kuyken Chris , van der Plas Klaas , Frederiks Kees , Williams Mike , Cockburn Colin
Published: December 2007

Slimhole drilling has long been regarded as means to reduce drilling costs and environmental effects through economies of scale and reduction of produced drill cuttings. However, its potential benefits have often been lost because of poor drilling performance and lack of well-placement capability in smaller holes. This is particularly true of brownfield environments, such as the North Sea, where tortuous multiple-target well paths require accurate and predictable directional capability in often-depleted reservoir sections. The development and effective deployment of a slim-hole rotary steerable system, (RSS), has changed this dramatically. Since initial field-testing in mid-2002, more than 30,000 ft of 6-in. hole has been drilled in the UK Continental Shelf alone. Performance has been exceptional, with average timesavings of over 60% compared with conventional drilling systems. Typical of this are wells on Shell U.K. Exploration and Production, (Shell Expros'), Brent and Cormorant Alpha fields, where up to 4850 ft has been drilled with near perfect well placement in a single run. Continued reduction of mature asset well costs through successful applications like these makes slimhole mature asset drilling economic and has the potential to extend drilling activity, field life and hence increase the ultimate recovery of the field.
Smørbukk Field: Fluid Modelling and Upscaling Issues to Simulate the Gas Cycling Process in Lower Tilje Formation
Authors: Pedersen Cecilie , Thibeau Sylvain
Published: December 2007

Smørbukk is an oil and gas condensate field, part of the Åsgard development in the Norwegian Sea in Norway.

The field consists in a vertical succession of various reservoirs of Jurassic age. Most of these reservoirs are layer cake, with sand bodies with several kilometers of horizontal extension versus only a few meters thickness. Lower Tilje formation consists of a volatile oil with a liquid rich gas cap.

The development scheme consists in two phases: A gas cycling period, currently taking place, with injected gas coming both from field produced gas and imported gas;A blow down phase, including gas back-production from the initial injectors.

In a previous paper, it was demonstrated that: –Without specific upscaling techniques, the two production phases request a different definition of the net to gross, leading to difficulties to simulate the entire production period;–The gas-oil ratio developments at the producers are highly sensitive to how the reservoir layering is derived from the heterogeneity captured at the wells.

The relevance of that work was limited, due to a simplified fluid description (live oil / wet gas fluid model) that could not accurately simulate the various processes taking place during a gas cycling scheme.

This paper presents new results, obtained with a compositional description of the fluids using an equation of state.

The key results are: –A comparison of various techniques to derive live oil / wet gas fluid models from the compositional one, and the implications in term of reservoir simulation results;–The set up, validation and implementation of an upscaling technique based on a comprehensive review of the physical phenomenon taking place in the reservoirs;–The fact that, using this technique, both production phases can be modeled consistently.
Otter - A Challenging Marginal Oil Field Development
Authors: Boyne Kevin , Horn Mark , Bertrane Didier , Fournie Francois , Cooper Terry , Quinn Patrick , Coudeville Fred , Buchan David , Allan Ken , Arnott Stuart
Published: December 2007

The Total E&P UK operated Otter Field is located in 184 m water depth in block 210/15a in the Northern North Sea area (partners Dana, Exxon Mobil and Shell Expro). It came onstream on schedule in October 2002, with a plateau production rate of over 30 000 bopd being achieved in May 2003. The economic development of this field has only been possible by using a combination of innovative drilling techniques, production technology and process systems to overcome the technical challenges posed, combined with the maximum use of existing infrastructures, to minimise Capex investment.

The three production wells are fitted with dual Electrical Submersible Pump (ESP) systems (a subsea first) and the total tieback distance is 21.5 km (a world record for ESP assisted tiebacks). These dual pump systems will allow significant production acceleration and improved recovery, while retaining lift redundancy and operational flexibility.

The Otter oil is exported in multiphase flow via Eider to North Cormorant. Both platforms are fitted with state of the art, minimum facility slug control systems. Eider will continue to operate in "lighthouse" mode (6- 8 personnel on board), a mode of operation developed by the Eider operator to extend field life by minimising field Opex. Prior to the sanction of the Otter project, it was planned to decommission Eider in 2005. Using Eider as a host for Otter has extended field life by around 5 years, increasing reserves recovery and deferring decommissioning expenditures.

The Otter development is therefore a successful example of a technically innovative and collaborative approach between the subsea tieback and host platform /infrastructure operators, partners and workforce. It provides a model for the future extension of North Sea Production, by using existing infrastructure, sharing expertise, and minimising costs.

The paper describes the Otter Development project and will focus on the technological innovations that have been deployed as part of this project, namely the subsea tie-back with downhole dual ESPs in the wells, the related flow assurance issues and mitigating measures (slug control systems, use of Kinetic Hydrate Inhibition facilities), their installation and other modifications required to accept Otter on the space constrained host Shell platforms. It also discusses the technical, commercial, contractual and risk management methodology employed by Total E&P UK during the project definition and sanction stages to facilitate the successful launch of this pioneering development.