bluuebunny/crossref_metadata_2025 huggingface dataset:
Reservoir Boundary Identification from Seismic Imaging for Well Test Analysis
Authors: Guérillot D. R. , Beydoun W. B.
Published: December 2007

Given a well test, the aim of this paper is to demonstrate that the range of possible reservoir boundaries derived from a seismic image is a valid constraint in the reservoir response.

A lens model was considered. Synthetic seismic and well test data were generated. The focus was to verify that the single phase well test response is sensitive to modifications of the reservoir boundaries derived from a poststack seismic depth image, all the other variables being fixed.

A specific prototype software was developed to implement the proposed methodology.
Analytical Expressions for Pseudoskin for Partially Penetrating Wells Under Various Reservoir Conditions
Authors: Gomes Edmond , Ambastha A. K.
Published: December 2007

Many times, oil reservoirs are accompanied by bottom-water zones and/or gas caps, and these reservoirs are produced using partially-penetrating wells. An extra pressure drop occurs around such wells during production because of partial penetration. Several correlations have been presented in the literature to estimate pseudoskin for a partially-penetrating well located in either a homogeneous or a layered reservoir with closed top and bottom boundaries. This study aims to develop new analytical expressions for pseudoskin for partially-penetrating wells in multi-layered reservoirs with both closed top and bottom boundaries, and with bottom-water zones and/or gas caps. A pseudosteady-state interlayer crossflow has been assumed in this study.

These new analytical expressions are simple and easy to use. Evaluaion of pseudoskin using these expressions requires a knowledge of two parameters when the top and the bottom boundaries are closed, and three parameters in the presence of a bottom-water zone or a gas cap, regardless of the number of layers. The estimated pseudoskin is very close to the actual pseudoskin obtained from the complete analytical solution. These new analytical expressions are also applicable to the corresponding homogeneous and single-layered cases. The estimated pseudoskin values have been compared with those estimated by other researchers. Effects of the open interval location, the presence of bottom-water zone and/or gas cap, and the layer refinement on pseudoskin have also been studied.
Integration of a Geological-Engineering Model With Production Performance: A Case Study at Patrick Draw Field, Wyoming
Authors: Chang M. M. , Szpakiewicz M. , Schatzinger R. , Jackson S. , Sharma Bijon , Tham M. , Lim F. H.
Published: December 2007

Analysis of production performance data from the Almond Formation in Patrick Draw Field, WY, a mesotidal shoreline barrier reservoir, was integrated with geological, geophysical, hydrogeochemical, and engineering information to generate an integrated reservoir model.

Reservoir compartments and flow barriers were indicated by high Hall plot slopes and discontinuities in saturations and properties of formation fluids. The flow barriers identified corresponded to areas of thin reservoir-quality sand and faults mapped from log and seismic information. In the northeastern portion of Patrick Draw Field, imbricated coquina beds and carbonate cemented zones degrade the reservoir quality, hinder lateral communication and result in poor sweep efficiency and low waterflood oil recovery. Formation water analysis data are relatively inexpensive and extremely useful in identifying reservoir compartments and are required for accurate calculation of oil saturations from resistivity logs. The wide variations of water salinity found in Patrick Draw Field indicated reservoir compartmentalization and demonstrated the degree of error in oil saturation calculations that may result if a uniform resistivity value is assumed.

Analysis of changes in producing gas-oil ratio, oil bank period, water breakthrough time, recovery efficiency, and rock-fluid properties indicated the location and nature of reservoir heterogeneities. Oil recovery near the gas cap was improved through pressure maintenance. Dykstra-Parsons coefficients wer not a good indicator of waterflood production performance in Patrick Draw Field. However, waterflood recovery efficiency increased with the average well permeability.
A New Modular Approach to Comprehensive Simulation of Horizontal Wells
Authors: Brekke Kristian , Johansen T. E. , Olufsen Rudi
Published: December 2007

The development in drilling and completion technology for horizontal wells has created new demands for enhanced comprehensive simulation methods. Wellbores with complex flow geometries are not easily implemented in commercially available simulation tools. A modular, comprehensive modelling of well and reservoir is proposed in this paper. The model consists of a detailed horizontal well flow simulator coupled to a reservoir simulator. The wellbore simulator is based on a network model which is capable of solving a broad range of possible flow configurations in the horizontal part of the well. The modular approach is facilitated by a coupling technique that reduces the requirement for iteration between the modules. The simulator is applied to high flowrate horizontal wells in thin oil zones with high permeability. Due to the flexibility in wellbore configuration, the simulator may be used to optimize well location, well path and completion approach. The coupling provides a detached wellbore simulation module which is reservoir simulator independent. The new simulation approach should be considered for horizontal wells where frictional pressure loss or geological inhomogeneities along the well are of importance to a well's production performance. The simulator will be used to evaluate completions with a complex flow configuration, potential cross-flow and for optimization of production and injection performance of wells in heterogeneous reservoirs.
Effect of Accelerational Pressure Drop in a Horizontal Wellbore
Authors: Ihara Masaru , Shimizu Nobutoshi
Published: December 2007

It is desirable that a horizontal well is properly designed with regard to the production performance, as well as the well completion. A rigorous analysis of flow hydrodynamics in a horizontal well was performed by including the accelerational pressure drop in the wellbore. This has been recognized as one of the unsolved, yet most important problems in the production engineering.

Pertinent experimental data were acquired with a large scale test facility, which was suitable for acquiring data on the relationship between the pressure drop along the wellbore and the fluid influx from the reservoir.

An initial mechanistic model was improved by including the accelerational pressure drop in the wellbore. As evident from the comparison of the experimental data with the model, the improved model described more rigorously the flow behavior m a horizontal well configuration. The model would be applied for field applications, by combining with the Inflow Performance Relationship (IPR) approach and the black oil model.
A Simplified Pseudo 3D Model to Evaluate Sand Production Risk in Deviated Cased Holes
Authors: Kessler Nicolas , Wang Yarlong , Santarelli F. J.
Published: December 2007

When comparing various wells on a given field in terms of sand production, it often happens that they display quite different behaviours: for example, deviated wells will produce sand whilst vertical ones won’t.

A major reason behind such an apparent paradox is the orientation of the well and its perforations in the in-situ stress field. Such a problem is usually studied by using complex non linear 3D Finite Element Models. In an attempt to make such an approach more flexible, this paper presents a simplified, semi quantitative analytical model able to evaluate sand production risks in cased holes with various deviations.

This pseudo 3D model, based on linear elasticity, confirms that sand production risk for a given perforation strongly depends on well deviation and on the orientation of the perforation in the plane orthogonal to the wellbore. A field case illustrates how the model can hence provide an understanding for observations which could have otherwise remained unexplained.

Finally, by introducing special failure criteria calibrated on hollow cylinder and cavity failure tests, an extension of the model is compared favourably to some 3D non linear numerical simulations in the case of a second field case. Because of its analytical nature, such an extension can easily be used in conjunction with logs in order to give a rather precise idea of the sand production risk on a newly drilled well.
Graduate Programs in Petroleum Engineering at Stanford University
Authors: Marsden Sullivan S. , Ramey Henry J. , Miller Frank G.
Published: December 2007

The described graduate degree programs in Petroleum Engineering at Stanford have been Petroleum Engineering at Stanford have been developed to meet the diverse needs of engineers and researchers involved with petroleum production. The M.S. program is essentially a production. The M.S. program is essentially a professional curriculum with only minor emphasis professional curriculum with only minor emphasis on research. The Ph.D. program emphasizes research and requires courses in engineering, science and mathematics. The Engineer's degree program, intermediate in goals and requirements, program, intermediate in goals and requirements, has one option which emphasizes professional engineering and another (the Management Option) which combines engineering and business courses and requires a thesis based on a combined engineering-economic study.

Introduction

Graduates of today's petroleum engineering departments may be expected to carry out a variety of tasks. While their undergraduate training can provide fundamental training for these, there is usually not enough time in a baccalaureate program to give much more than an introduction to production and reservoir engineering methods. Specialized training in these fields as well as in research must be left for the graduate level. Because the goals of graduate study are multipurpose and generally different from those of undergraduate study, we have found that several distinct graduate programs are necessary. We would like to describe programs are necessary. We would like to describe those which have been devised in our petroleum engineering department with the hope that this description may be of interest and help to others.

A dozen years ago most of our graduate students were M.S. candidates who had received their B.S. from our Department the previous year and so the undergraduate and graduate programs were closely related. Now most of our programs were closely related. Now most of our graduate students are Ph.D. candidates who have either taken their M.S. degree here or more usually, obtained it elsewhere. Thus our undergraduate courses are often taken by graduate students as electives to make up deficiencies. These courses are also taken by our own undergraduates as well as by students from other departments.

In addition to the M.S. and Ph.D. degree programs which require graduate residency of programs which require graduate residency of one and three years, respectively, we also have two programs leading to professional Petroleum Engineer degrees, and each requires two years of graduate residency.
Fracturing of High-Permeability Formations: Mechanical Properties Correlations
Authors: Morales R. H. , Marcinew R. P.
Published: December 2007

Geological and mechanical laboratory experiments were conducted on several core samples in order to characterize the material behavior and generate data for the design of hydraulic fracturing treatments for high-permeability formations. Photomicrographs of thin sections were used to classify the specimens according to their granular constitution and pétrographie components.

The results of evaluations of fracture toughness, permeability, porosity, static and dynamic Young’s modulus and Poisson’s ratio are presented. Based on linear regression analysis, correlations relating static to dynamic Young’s modulus were derived. The error between the predicted and measured values was minimized by dividing the samples into three porosity groups.
Unconventional Acid Design Used to Stimulate Sandstone Reservoirs in the Gulf of Mexico
Authors: Ewing J. W. , Clements Todd , Ali Syed , Dunlap D. D.
Published: December 2007

Formation damage from the migration of fines has historically been the cause of rapid production decline at the Eugene Island 361 field in the Gulf of Mexico. Conventional acid systems have been used with limited success to stimulate these oil reservoirs. An acid system was needed to address complexities that are seen in this field and in many other Gulf of Mexico sandstones. These complexities include high feldspar and clay content, a high percentage of silt-sized particles, and low bottomhole temperatures.

Current acidizing techniques in the Gulf of Mexico generally employ the use of either 12:3% HCl:HF or 7.5%:1.5% HCl:HF acids. However, the abundance of clays and feldspars occurring in this area hinder the long term success of these conventional treatments. The conventional systems only partially remove near wellbore fines causing these wells to realize only temporary stimulation benefits. An unconventional system employing various combinations of HCl:HF acids has proved to provide the best production response and economic success. This paper details the laboratory and field evidence of this unconventional treatment’s success.
The Optimum Injection Rate for Matrix Acidizing of Carbonate Formations
Authors: Wang Y. , Hill A. D. , Schechter R. S.
Published: December 2007

Our main result is the discovery of an optimum acid injection rate to obtain acid breakthrough in linear corefloods of carbonates using a minimum total acid volume. Low rates result in acid spending at the core surface while high rates result in the formation of multiple, highly ramified wormholes. At the optimum intermediate rate, a single, small wormhole penetrates the core.

The optimum acid rate is found to be a function of the rock composition and reaction temperature as well as the pore size distribution of the virgin formation rock. All of these factors are included in the theory developed here. This theory provides a quantitative prediction of the optimum rate. The practical ramifications of the results are also considered.
API Tank Vapors Project
Authors: Choi M. S.
Published: December 2007

The E&P industry has tens of thousands of field storage tanks in produced oil service. Most of the tanks do not have vapor recovery and the evolved gases are vented to the atmosphere. With the implementation of the 1990 Clean Air Act Amendments (CAAA), the industry is faced with the need to quantify its emissions. These emissions inventories must be broken down by components due to the distinction placed upon the category of Hazardous Air Pollutant (HAP).

In addition to HAPs, Volatile Organic Compound (VOC) emissions also need to be quantified for purposes of regulatory reporting and as design basis for vapor recovery units (VRU). Many operators have attempted to measure emissions directly. However high cost and erratic results that can be directly attributed to the nature of the tank system have discouraged the use of field measurement as a viable option for estimating emissions.

In June of 1993, an American Petroleum Institute (API) project was initiated to develop an estimation method for HAP and VOC emissions from oil field storage tanks. The method is based on the use of computer process simulation techniques, predicated on minimal and easy-to-acquire field data and laboratory analyses. This paper describes the methodology that will be used and the deliverables that are expected from the joint industry effort.
Fracture Height Containment with Continuum Damage Mechanics
Authors: Valkó Peter , Economides M. J. , Leoben Mining U.
Published: December 2007

A recently introduced fracture propagation model, incorporating continuum damage mechanics (CDM) has been found as an adequate and consistent vehicle to predict both the level and trend of the net pressure. In this paper the CDM concept is applied to a pseudo-3D propagation model to describe height growth. In contrast to equilibrium theory, both the vertical stress profile and the (possible different) CDM coefficients are responsible for the final fracture morphology. This model is not burdened by the frequent capricious behavior of linear elastic fracture mechanics (LEFM) based models. The paper presents the model development and discusses the computational results. A comparison is made to the results of other fracture simulators published in a recent comparative study. A procedure is suggested to obtain the necessary CDM parameters from minifrac tests.
Prediction of the Oil Rate Increment With Water Profile Control by Polymer Injection
Authors: Giudicelli C. B. , Truchetet R. A.
Published: December 2007

The efficiency of a water profile control treatment by polymer injection is usually predicted by laboratory measurements.

An analytical model is described which allows calculations of the incremental oil rate The model is based on a two-layer system and integrates both laboratory results and reservoir characteristics. It shows that the basic principle of water profile control by polymers is the reduction of productivity of the water-flooded zones.

This model handles as well uncertainty on the various parameters involved through a probabilistic approach which provides uncertainty brackets on the results.

A field data analysis is completely performed before application of the model and results are presented.
Linking Universal Kriging and Reservoir History Matching
Authors: Watkins A. J.
Published: December 2007

This paper describes how the framework developed for universal kriging can accommodate a general formulation of the reservoir history matching problem. We illustrate this framework with simple examples, and then show that the specification of the required covariances and correlations provides an opportunity to introduce explicitly some pertinent reservoir engineering knowledge into history matching. We then briefly consider the elicitation of this information in the form of parameter values in functional forms for covariances, and discuss how the specification of weights can influence calculations, and hence convergence to an optimal history match. We conclude with a review of some of the available diagnostics and a summary on practical applications of the framework.
Visualization of Rock Samples in Their Natural State Using Environmental Scanning Electron Microscope
Authors: Gauchet Renaud , Cheneviere Pascal , Tricart J- P.
Published: December 2007

Among the new tools which have been developped recently in the area of rock characterization at the microscale level, Environmental Scanning Electron Microscope (ESEM) is particularly relevant in petroleum technology. This technique allows visualization of rock samples in their natural state in presence of fluid distribution, and during microdynamic experiments in presence of both brine and oil. In addition to this dynamical process recording, imaging and elementary analysis are also available.

This new technique has been used in our laboratories to perform various experiments on gas/liquid and liquid/liquid systems, on core samples coming from different reservoirs known for their wettability behavior.

First, a set of condensation-imbibition tests on shaly samples were carried out to investigate the anticipated preferential affinity for water of illite versus kaolinite. This direct visualization of contact angles and imbibition effectiveness in an air/brine system showed a clear affinity of clays for brine and an imbibition process mainly controlled by shape factors.

Secondly, a step by step visualization of fluids distribution in an oil/brine system during initial water saturation or residual oil saturation installation has been performed. This allowed to visualize oil and brine distribution in the case of three reservoir core samples, one water wet, one intermediate wet and one oil wet. A series of images illustrates some of the oil/brine displacement mechanisms at the microscale.
Reservoir Management in Tertiary CO2 Floods
Authors: Merchant D. H. , Thakur S. C.
Published: December 2007

Since 1984, Amoco has operated four major enhanced oil recovery projects using CO2 in West Texas. Due to the high cost of CO2 injectant, the economic success of these floods depends on the ability to properly monitor and manage CO2 utilization. This paper describes a new approach to the surveillance and management of the Slaughter Estate Unit CO2 flood. The method described here involves real-time monitoring on a well-by-well, pattern-by-pattern basis by displaying raw as well as processed data using the "Montage" concept. Using this concept, injection, production, and other data from a well or a group of wells can be viewed simultaneously by zooming into any area of the field. Inter-well communication and gas cycling can be recognized quickly and changes in operating variables can be made. As a result, the economic performance of a CO2 flood can be optimized by making prompt adjustments to gas-water ratio, CO2 and water half-cycle slug sizes, and injection and production well pressures.
Is Parallel Computing Ready for Reservoir Simulation? A Critical Analysis of the State of the Art
Authors: Killough J. E.
Published: December 2007

Recently the lure of scalable distributed memory parallel computing with hundreds or even thousands of inexpensive, but powerful, RISC-based processors has resulted in a significant effort in the development of software for petroleum engineering and seismic applications. Unfortunately, few if any applications have found their way into a production environment from the reservoir engineering perspective. Several hurdles remain to be overcome if parallel computing is to become commonplace as a tool for applications. This article addresses three areas of concern for a reservoir simulation: load balancing, data structures, and linear equation solutions. Examples from real reservoir simulations and possible solutions for several situations are discussed.
Tracer Transport in Characterization of Dual-Porosity Reservoirs
Authors: Shinta A. A. , Kazemi Hossein
Published: December 2007

A single-porosity model (SPM) for the tracer response analysis in fractured reservoirs is developed in this paper. This new technique is useful in characterizing fractures in terms of flow anisotropy and quantifying fractures properties such as porosity and permeability. Specifically, tracer response has good resolution and, therefore, its analysis can determine the orientation and conductivity of high permeability fractured systems in the reservoir. This information is highly desirable in improved oil recovery planning and management. The simulator used here is five-point, nine-point finite-difference, two-dimension and two-phase (oil and water) model. In addition to SPM, the simulator conducts a single block simulation (SBS) and conventional dual-porosity calculations. Several options to eliminate or minimize grid orientation effect (GOE) in fractured and unfractured reservoirs are included. These nine-point options appropriately account for the permeability tensor and flow channeling. The SPM is used successfully to characterize an anisotropic confined five-spot pattern in an actual field test.
Effects of Recent Relative Permeability Data on CO2 Flood Modeling
Authors: Prieditis John , Brugman R. J.
Published: December 2007

Results from laboratory tertiary CO2 flooding studies conducted at representative reservoir conditions are becoming available. Predicted CO2 flood performance can be significantly changed by using this data in reservoir models. The laboratory data includes water and oil relative permeabilities when the water saturation is decreasing, residual oil saturations to a miscible flood, residual CO2 saturations, and CO2 relative permeabilities. Predicted oil recovery, CO2 production, and breakthrough times are all influenced.

Unfortunately, much of this data cannot be used in most presently available commercial reservoir simulators. Additionally, there is uncertainty about the proper form for the relative permeability of the miscible (non-aqueous) phase. For example, should the miscible phase relative permeability be based on the gas, oil, or solvent relative permeability or some combination? Texaco has developed a mixing parameter based reservoir simulator that not only uses the new relative permeability data but also incorporates different forms for the miscible phase relative permeability.

This paper describes how the recently available laboratory data and the form of the miscible relative permeability formulation affect predicted CO2 flood performance. Results presented show the importance of using the laboratory data and show what changes in existing simulators may be advisable.
Gas Condensate Well Testing Under the Influence of High-Velocity Flow
Authors: Hernández Héctor , Samaniego Fernando , Camacho Rodolfo G. , Galindo Agustín
Published: December 2007

This paper presents the results of a systematic study of the influence of high- velocity flow on the interpretation of transient gas condensate well tests. A one dimensional radial fully implicit compositional model using the Forchheimer equation was used to obtain the results presented in this work. Drawdown and buildup tests at constant mass rate were simulated. The simulator was carefully checked, since no solutions for gas condensate flow are available in the literature that consider high-velocity flow. Among these tests, in accordance to the method of Camacho et. al., multiphase high-velocity results were graphed in terms of d ppwd/d ln tD vs 1/(tD)1/2, presenting a. positive slope, characteristic of high-velocity flow, that extrapolates correctly to the 0.5 interception value corresponding to Darcy flow. It was found that drawdown solutions graphed in terms of the sandface dimensionless pseudopressure vs log tD show for large times the characteristic one phase slope of 1.151. As expected, high-velocity effects result in an earlier appearance of the condensate phase in the reservoir. It was also found, as already mentioned, that results of this study when properly expressed in terms of pseudopressure show the characteristic behavior for the high-velocity monophasic flow method of Camacho et. al., which allows the estimation of the high-velocity pseudoskin factor and flow capacity. Thus, this method is also valid for conditions of this study as a diagnostic tool for high-velocity flow. It is also demonstrated that the mobility function λt(pw) can be estimated from the derivative of the pressure data.
Simulated Annealing for Relative Permeability and Capillary Pressure From Unsteady-State Non-Darcy Displacement
Authors: Ucan Sezai , Civan Faruk , Evans R. D.
Published: December 2007

An interpretation method using simulated annealing for simultaneous determination of relative permeability and capillary pressure from non-Darcy gas/liquid laboratory corefloods is presented. The effects of gas solubility in liquid and variable rock and fluid properties are considered.

The methodology is first tested by using imbibition and drainage experimental data in the Darcy flow regime and for oil/water and gas/water systems. Relative permeability and capillary pressure curves are generated under different constraints of measurements of core displacement data. Estimated flow function properties are compared with each other. Then the application of the method is illustrated for non-Darcy fluid displacement cases. The method presented here provide discrete values of relative permeabilities and capillary pressure in contrast to spline and other types of prescribed functional representations reported in the literature.

It is demonstrated that entirely different relative permeability and capillary pressure models, such as those based on spline and other types of functional representations, can also be used to match the same recovery performance. If only the recovery curves and overall pressure differential data are used, flow properties can not be obtained uniquely. However, the flow properties can be determined uniquely when transient-state internal saturation profiles and the overall pressure differential data are used. The advantage and convenience of the simulated annealing optimization algorithm are that it does not require the evaluation of first or second gradients of the objective function. Thus, the simulated annealing method converges in all cases without increasing the computational effort and time significantly.
Management of Environmental Impact Studies: A Perspective on the Exxon Valdez Environmental Assessment
Authors: Maki A. W. , Burns W. A. , Bence T. E.
Published: December 2007

New and evolving environmental laws and regulations impose substantial costs and greater potential liabilities on industry. These standards on emissions and assessments of impacts place increasing importance on scientifically based environmental studies. Moreover, technological improvements have provided measurement techniques that detect hydrocarbons that are far below levels significant to the environment. In such situations, it is important for companies and government agencies to design and implement environmental programs that can distinguish meaningful environmental effects due to effluent discharges and spills from those effects associated with natural ecological variation or numerous other factors influencing ecosystems.

This paper describes the environmental-assessment process implemented following the Exxon Valdez spill. This is the most extensively studied oil spill in history and the conclusions drawn from the studies may have a significant effect on future regulations and liability. Unquestionably, large spills can have acute effects; the issue is the ecological significance and duration of those effects.

Conflicting claims have been made about the seventy and longevity of spill impacts in the case of the Valdez spill. This paper summarizes studies that show shorelines, birds, and mammals have essentially recovered in the four years following the spill. They further demonstrate that fish, the most important commercial and subsistence resource present in the area, were minimally impacted.

The paper highlights the pitfalls of studies that do not carefully evaluate spill impacts by using sophisticated and sound scientific techniques or which fail to consider spill impacts within the context of natural variability and other environmental factors.
Protection Measures for Subsea Structures Against External Hazards
Authors: Copsey N. R. , Johnson S. E.
Published: December 2007

This paper reviews the design of subsea developments in relation to possible external hazards. The hazards considered are fishing gear impact, dropped objects and anchor lines. Alternative protection measures are discussed and suggestions are made for the most suitable design approaches over a range of practical situations.

The emphasis in this work is on the application of risk analysis methods to produce ‘fit-for purpose’ designs – avoiding unwarranted costs from over-conservative approaches.
Use of Economic Measures as the Criteria for Optimising Functional Blocks and the Selection of Development Concepts
Authors: Holsen Malvin , King S. D. J. , Steine Gunlaug
Published: December 2007

The paper presents a methodology for optimising offshore hydrocarbon production developments, employing NPV/LCC as an economic selection criteria, including production revenue, throughout all project phases. Combining CAPEX, OPEX and Production Performance into Net Present Value (NPV) gives an opportunity to base decisions upon optimised economics over the field lifetime.

In the early phases of a field development, the methodology analyse all possible solutions systematically. The method analyses the major functions necessary for field production, selecting functional solutions with highest economical potential, and combining the functions into total field development solutions. The methodology utilises aggregated data for CAPEX and OPEX ( a top-down approach), and is often referred to as the ‘Screening Methodology’.
Impregnated Bit Technology Improves Drilling Efficiency in North Sea Conglomerates
Authors: Galletta Antonino , Wapshaw K.G.C. , Wrighton Timothy
Published: December 2007

SPE Members

Historically, the Upper Jurassic Brae conglomerates intrinsic to North Sea Block 16/17 have been drilled with IADC 517 to 617 type roller cone bits. Unfortunately, excessive wear to the cutting structure and gauge area of these bits dramatically limited their useful life and made them uneconomical. Runs shorter than 100 ft with penetration rates as low as 4 ft/hr was not uncommon with these bits. This was true even for roller cone rock bits incorporating enhanced gauge protection.

The decision to employ fixed cutter bits in Block 16/17 was initially frustrated with the inability of existing designs to effectively drill the conglomerates. However, a new fixed cutter design concept utilizing impregnated grit-sized diamonds has greatly improved drilling performance with substantially lower cost per foot.

Field tests have shown average penetration rates of more than 1 5 ft/hr with bit life averaging 400 ft. Penetration rates have remained steady throughout the target interval. Further, no significant gauge wear has been observed, despite the fact the bits were run on turbines.

This paper describes the development of the IADC M841 class fixed cutter bit and its application in these formations. The cost savings achieved with these bits and the future potential of the M841 impregnated diamond drill bit will be analyzed. The laboratory testing leading up to the development of the impregnated diamond bit will be detailed.

Introduction

Block 1 6/1 7, also known as the T-Block, is located about 120 miles from Aberdeen in the Central North Sea (Fig. 1). Phillips Petroleum made the first discovery in the region in 1976 and since then four distinct fields have been identified: Tiffany, Toni, Thelma, and South East Thelma (Fig. 2). Since assuming operatorship of the block in 1986, Agip UK has thus far decided to develop the Tiffany and Toni fields. To date, 20 exploration and appraisal wells have been drilled on the block. Four development wells have been pre-drilled for the Tiffany platform, which became operational in the summer of 1993, and five wells have been drilled through a subsea template installed for the Toni development.

Historically, the Brae conglomerates of the Upper Jurassic sequence of the Central North Sea have proved extremely difficult to drill. The unique combination of a hard and abrasive sandstone matrix with a pebble and occasional breccia conglomerate found in Block 16/17 has made it a particularly difficult area to drill. The formations encountered there have proved impenetrable for both insert roller cone or standard fixed cutter bits.

Since 1 988, Agip UK has been involved in an extensive program to develop a fixed cutter bit capable of drilling the difficult Brae conglomerates of Block 16/17. What resulted was a partnership with a bit manufacturer, which led to the successful development of the IADC M841 type impregnated diamond fixed cutter drill bit,

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An Experimental Investigation of the Formation Damage Caused by Produced Oily Water Injection
Authors: Zhang N. S. , Somerville J. M. , Todd A. C.
Published: December 2007

This paper presents results from an experimental study on formation damage associated with simulated produced oily water injection. Core flooding experiments were carried out with simulated produced oily water containing 40 to 500 ppm crude oil at 1-15 ppm solids (1-10 μm mean diameter) dispersed in brine. The formation damage along the length of a core was investigated and a number of parameters contributing to permeability decline were evaluated.

The results indicate that produced oily water containing oil droplets and solid particles can contribute to the permeability decline observed in the cores. The most severe decline occurred in the first 10-15 mm of the core. Oil droplets with a dimension significantly less than the pore throat diameter also led to permeability decline. The permeability alteration resulting from a combination of both oil droplets and solid particles is more severe than obtained from the systems individually.
Compact Weight-Down Gravel-Pack Floater System with Absolute Isolation System
Authors: Echols R. H. , Thomas P. T. , Oncale R. P. , Fischer Dan , Hubble T. A. , Park D. A.
Published: December 2007

Completion fluids that are introduced to the reservoir during gravel-pack operations often cause formation damage that can substantially reduce production potentials. Most gravel-pack operations employ fluid loss preventive methods to manage this problem. However, in the scenario in which gravel packing is attempted from a floating vessel such as a semisubmersible rig or drill ship, an additional problem, rig heave (wave motion), must also be addressed; the effects of rig heave compound fluid-loss problems and require additional controls in the gravel pack system. Conventional systems have attempted to manage the problem by adding seals and collets for locating the workstring; however, these additions considerably increase the cost of the systems and have not adequately addressed both gravel packing and fluid loss prevention needs.

This paper will describe a new compact weight-down gravel pack system that has been successfully used on floating vessels for gravel packing. The traditional systems that have been used on floating vessels for the same purpose will also be described. Case histories will illustrate how the new system provides solutions to the difficulties normally experienced in offshore gravel packing. Of particular interest are the following advantages that use of the new system provides:

Operational costs are reduced since less rig time is required. Tool reliability is enhanced because of the simplicity of the system. No chemicals are required for fluid-loss prevention. Formation exposure to fluid loss immediately after gravel packing is in most cases eliminated.

Other applications are being proposed for the new system, and these will also be reviewed.
Geology and Hydrocarbon Potencial arctic regions of the West Siberian basin and the Kara sea
Authors: Girshgorn L. , Nemchenkc N. , Rovenskaya A.
Published: December 2007

The northern part of the West Siberian province is mainly a gas producing area. Onshore, gas forms 80% of hydrocarbon production and potential recoverable reserves are estimated at Trillions of cubic meters. The hydrocarbon potential of offshore extensions of West Siberian producing basins may be equally high. Kara Sea basin is a likely target for future exploration interest and development activity.

Arctic part of West Siberian oil-gas basin, including. offshore in the Kara-Sea and West of the Enisei-Hatang depression, is characterized by some peculiarities of geological structure and history and as consequence specificity of oil-gas bearing, that distinguishes this area from the rest West Siberia basin. This region has natural geographical bounderies: on the South it is the main watershead of the plain – Siberian Uvali, on the North it is the continental threshold in the Kara-Sea, on the West and East – these are exposed Hercynian and Cimmerian folded systems.

Specificity of the region may not be detected quite definitely in Geological Map (Fig 1), as the Cenozoic and Cretaceous sediments overlap the tectonicaly heterogeneous northern and southern parts of West Siberian plain by the single common cover. More clear picture gives the Scheme of "Major structures and age of the cover" (Fig 2).
Primary Design Considerations for a Packerless Annular Safety Valve (ASV) System for the North Sea
Authors: Taylor R. W. , Longbottom J. R. , Adams M. P. , White P. M.
Published: December 2007

The trend in the North Sea has been toward installing annular safety valve (ASV) systems for tension leg platform (TLP) completions or for gas-lifted platform production wells. To satisfy the requirements for a highly reliable annular safety system for the Norske Shell Draugen project and an impending Norwegian TLP completion project for the North Sea area, tests were initiated to investigate the feasibility of a polished bore receptacle (PBR)-based ASV system. The nipple system has the capability to handle high hang-weight and/or thermally-induced loads, and the PBR nipple, pre-installed in the casing string, will permit a variety of completion designs that can be determined later in the welldevelopment cycle. Testing verified that 1) only a minimal pressure drop occurred through the system, 2) there were no compatibility problems between drilling/cementing operations and the PBR system, and 3) a PBR casing nipple assembly to anchor an ASV system has the capability to provide a viable alternative to use of a mechanical ASV packer and its related seals.
A Goal-Setting Approach to Offshore Regulations
Authors: Taylor B. G. S.
Published: December 2007

The Offshore Installations (Safety Case) Regulations(1) represent a major step forward in the regulation of offshore safety. Operating Companies have a duty to conform with a Safety Management System and Safety Case prepared by themselves and which has been accepted by the Health & Safety Executive. This approach moves the UK Offshore Industry away from the prescriptive requirements of the past towards a goal-setting approach supported by non-mandatory Guidance.

To underpin the Safety Case Regulations, the Health & Safety Executive (HSE) proposes to enact further offshore specific regulations revoking or replacing existing prescriptive requirements. The new regulations will be expressed, wherever possible, in terms of safety objectives or goals to be achieved, rather than specifying particular precautions. The intention is for these goal-setting regulations to be supported by non-mandatory Guidance to be developed by HSE and Industry.

These aims are in accord with Lord Cullen's recommendations and the Industry takes no exception to them. Nevertheless the Industry has expressed concern that the new Regulations, if not carefully drafted, could undermine the primacy of the Safety Case Regulation rather than support it.

The UK Offshore Operators Association (UKOOA) has played a leading role in informal consultations with HSE and will contribute fully to the debate during the formal consultation phase on these regulations to ensure that they are compatible with and support the Safety Case Regulations which the Industry firmly believes should remain the foundation for improved safety offshore.
Partnering Between a Major Operator and Lead Contractors for Drilling and Well Services Activity
Authors: Schaafsma M. G.
Published: December 2007

Shell U.K. Exploration and Production, Operator in the U.K. sector of the North Sea for Shell and Esso, has adopted a corporate strategy in line with the Drilling in the Nineties concept proposed by Shell Internationale Petroleum Maatschappij B.V. (SIPM) for all Shell Operating Companies. Within Shell Expro the Drilling in the Nineties concept has been broadened to incorporate the drilling, well services and equipment supply areas with the resultant name change to Well Engineering in the Nineties.

This strategy has now been implemented and has substantially changed the modus operandi between operator and contractor with a strong emphasis on long term partnership relations with lead contractors.

This paper summarises the strategy that has been developed, the implications of implementing this strategy; the implications to both a major operator and numerous contractor suppliers; the results to date; and the course of future partnership relations.
Partnering on the Forties Field
Authors: Hazlett K. P. , Helliwell Dennis
Published: December 2007

Four years ago BP was forecasting production from the huge Forties Field in the North Sea would become uneconomic by the mid nineties and progressive shutdown would commence around 1995-96 with the last platform being decommissioned by the year 2000.

A challenge was set to extend the life of the field through to 2010, and as a result of a major review by BP of the cost efficiency of its operations the challenge is beginning to be met. Forties production can now remain viable for much longer than expected in 1989, even after a fall in oil price from $25 to $18 per barrel. Not least of the influences making this extended life expectancy possible are the cost advantages promoted by an innovative Partnering venture between BP as operating company and Brown & Root as contractor.

The Forties Oil Field was discovered in 1970, 110 miles ENE of Aberdeen in 110 metres of water. Recoverable reserves were then estimated at 1.8 billion barrels. Four platforms were designed, constructed and installed and first oil was produced in September in 1975. Peak production of 500,000 barrels per day was reached in May 1978. A fifth platform was installed in 1986 and the 2 billionth barrel of oil was produced in April 1989, an achievement far in excess of original predictions. The estimate for recoverable reserves today stands at 2.5 billion barrels with the current production rate being 140 mbd.
Saving Thistle's Bacon: The Role of Reservoir Management in Optimising a High Watercut Field
Authors: Clyne P. A. , Bajsarowicz C. J. , Jones Kevin , Milne Donald , Richardson S. M.
Published: December 2007

Abandonment timing for Thistle is uncertain, and the aim of reservoir management is to accelerate reserves so that value is maximised prior to a target date. In an environment of tight expenditure control, the focus has shifted from large field studies to well reviews, and from infill drilling to rccompletion.
Taking the Forties Field to 2010
Authors: Thomson R. L. , Howden A. B. , Neill T. H. , Lindsay S. T.
Published: December 2007

The continued success of BP's Forties Field, is crucially dependant upon fundamental changes in working practices and the development of world class operating and maintenance techniques. For the past two years, the Forties Team have taken the concept of an empowered work force from its infancy through to adolescence. At the same time, one of the five platform teams has tackled the issue of developing excellent standards of Total Productive Maintenance (TPM) in the offshore environment. TPM is an application of operator autonomous maintenance, developed in the West and perfected by the Japanese. We believe that this is the first ever application of TPM offshore and the first "whole team" approach to empowerment. The visionary aim is to be the role model in the operation of a declining oil field.

This paper describes the way in which empowered teams have been put in place in Forties. Examples of how organisational and cultural challenges have been successfully addressed, are illustrated. The application of TPM offshore is described, from initiation, introduction, development and onwards to the goal of self sustaining improvement from within the teams. Through the efforts of the empowered teams and implementation of world class systems, the aim of extending the Field life of Forties from 2003 to 2010 and beyond, is now seen to be a reality.
A Three-Dimensional Hydraulic Propagation Theory Simulating Fracture Growth Simultaneously from Two Sets of Perforation
Authors: Lee W. S.
Published: December 2007

When planning a fracture treatment where more than one set of pay zones will be perforated, a designer must consider that multiple fractures will initiate simultaneously and later merge into a lesser number of fractures. Unfortunately, almost all published three-dimensional fracture simulation papers assume that there is only one fracture made during the entire fracturing process. Consequently, if more than one set of perforations exists, some averaging techniques must be used that reduce the accuracy of the simulation. This simplifying assumption is often made due to the mathematical complexity of dealing with multiple fractures with or without merging.

This paper represents the first effort to solve this complex problem. In this paper, we discuss a simple case with only two sets of perforation zones; in the future, it is planned to extend the problem to more sets of perforations.