bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinct Element Analysis of Borehole Instability in Fractured Petroleum Reservoir Seal Formation
Authors: Nicolson J. P. W. , Hunt S. P.
Published: December 2007

This work presents the analysis of a borehole instability case at 2km in a seal formation within the oil field environment. Field observations of severe borehole instabilities are given. The factors causing this instability are observed as being due to cyclic mud pressure loading, drilling induced damage, wellbore orientation and fault set intersection at the wellbore.

Borehole breakout data both from image logs and calliper data has been used to determine the in-situ stress field. The minimum principal stress magnitude has been obtained using leak off testing, extended leak off testing through the analysis of borehole breathing during drilling with losses. The data has been analysed using non-parametric statistical techniques to determine the complete stress tensor. Fault property and in-situ rock mass data has been obtained from triaxial and shear box testing.

For this study the distinct element method (UDEC) has been used in 2D to study the wellbore stability under dynamic (fluid flow) conditions. Factors taken into account include fault, fracture and bedding surface orientation, fracture parameters, in-situ stress conditions, cyclic mud pressure loading, initial drilling induced damage and well bore orientation. The study has investigated the behaviour of a synthetic rock mass containing low permeability rock blocks separated by low to very low permeability joints.

It has been observed that all parameters influence the level of stability but using a prolonged delay in mud pressure reduction, stability can be maintained, also it is possible to select optimum wellbore orientation in advance using the numerical procedures.
A Case Study of Massive Hydraulic Fracturing in An Ultra-deep Gas Well
Authors: Ding Yunhong , Jiang Tingxue , Wang Yongli , Ping Sun , Xu Zejun , Wang Xin , Zeng Bin
Published: December 2007

Proposal

A case study of hydraulic fracturing has been performed in details in Jing-70 gas well located in north china oil field with the depth larger than 4000 meters. In the past, such kind of gas wells couldn't be fractured successfully as a result of early tip-screenout.Our study is on the base of past fracturing experience, and a lot of improvements have been made. The main character of our fracturing design is as following:1)core test of stress sensitivity is used in performance prediction model and determination of bottom flowing pressure;2) mini-frac is performed in order to get loss coefficient more precisely;3)large scale of proppant volume and high proppant concentration are used as principles;4)a new surfactant named DL-10 is developed to increase flowing back velosity;5)long term conductivity is inputted in to a new developed gas reservoir model so as to perform optimization more scientifically;6)multi-stage proppant pumping schedule is used so as to get an expected propped profile;7)pumping rate is requested to increase higher and higher under the limit of wellhead pressure according to three dimensional fracture propagation model;8)liquid nitrogen is used in the course of fracturing in order to enhance flowing back of fracturing fluid after shut-in;9)forced closure technique is utilized;10)systematic field quality control is used to ensure fracturing treatment to follow the design plan, and some modifications is allowed according to the change of treatment situation.After that, the well is hydraulically fractured successfully with 67 tons of proppant and sand to liquid ratio as high as 30%,which is the highest record in ultra-deep gas wells in north china. And post evaluation is performed completely including net pressure analysis. Overall, the fracturing design, treatment and post evaluation discussed in the paper for ultra-deep gas wells has a great significance in gas wells’ stimulation and development as well.
Downhole Formation Fluid Identification in a Mature Multi-Layer Reservoir: A Case Study of an Advanced Wireline Formation Tester and Operational Practices for Highly Depleted Reservoir Evaluation
Authors: Ferment Denis , Gautama Yudowicana , Rourke Marvin , Guergueb Nacer , Singh Jorawar
Published: December 2007

The highly complex, stacked and multi-layered gas reservoirs found in the Mahakam delta of East Kalimantan present a challenge for both drilling and formation evaluation. Many of the mature producing reservoir layers are at low pressure today; but the presence of certain over-pressured intervals means drilling is essential with high mud weights. Drilling with high mud weights can lead to high differential pressures, as much as 5000 psi, between the wellbore mud system and the formation fluid pressures. A significant part of the formation evaluation in the Kutei basin [h1]requires formation fluid identification using a pumpout wireline formation tester (PWFT). The primary objectives are to obtain a measurement of the formation pressure, identification of the formation fluids, and the determination of fluid mobility. The PWFT tool operates by controlled pumping of formation fluid from a sample probe, which is positioned adjacent to the reservoir interval, through a fluid analyzer and out to the wellbore. Fluid property measurements and filtrate contamination and identification are accomplished with a new Magnetic Resonance Imaging Laboratory (MRILab™) fluid analyzer. Due to the difficult conditions encountered in the Mahakam delta, the sampling times ordinarily required to pumpout and collect uncontaminated PVT samples were not possible. This paper demonstrates the techniques that were developed where the MRILab could quickly identify the formation fluid in situ while pumping and eliminate the need to collect and retrieve a sample.

In this paper, we use field examples from operations involving the Reservoir Description Tool (RDT™) and the MRILab™. The RDT tool employs new features that enable enhanced operational practices to improve formation testing in this difficult environment. The tool features demonstrated in this paper include dual probes vertically spaced seven inches apart with isolation valves and independent pressure gauges for each probe, a new pump module that can operate up to 6000 psi differential, and an MRILab fluid analysis module. Operational practices discussed include preventing tool plugging, faster testing in tight zones, and precise tool positioning.
Integration of LWD and Wireline Array Technologies to Improve Estimation of Hydrocarbon Reserves
Authors: Frenkel Michael A. , Nuic Ivo , Walker Mike J. , Wolters Frank L.
Published: December 2007

This paper presents a new method for determining formation resistivity via sequential interpretation of the LWD and Wireline (WL) resistivity logs. The LWD logs can be used to determine the Rt, but they may not contain enough information to accurately determine parameters of invaded zones. The inversion-based interpretation of the WL Array resistivity logs provides a direct way of determining the hydrocarbon-bearing formation model. However, interpretation of WL data may be unstable and provide an incorrect equivalent solution due to a strong non-uniqueness of the inverse problem. To find the true model from an unlimited number of equivalent solutions, we propose a stable method that leads to a gradual increase of the formation model complexity.

The major steps are: Estimation of Rt using deep-reading LWD data inversion.Estimation of Rxo using an Rxo WL log.Estimation of Lxo using WL data inversion.Simultaneous corrections of the final model parameters using WL data inversion.

To establish the effectiveness of our method, we first successfully tested it on 2-D and 3-D benchmark models. To examine the practical validity of the method, we applied it to LWD induction data and the Array Lateral Log WL data acquired in a salt-saturated mud environment in a deviated well located in the South China Sea. Our objective was accurate determination of hydrocarbon saturations. Application of our method allowed us to accurately determine the formation resistivity and translate it directly to accurate Sw estimates. We demonstrate that the suggested method provides a lower Sw saturation than the sole WL data interpretation.
An Improved Approach to Estimating True Reservoir Temperature From Transient Temperature Data
Authors: Roux Brian , Sanyal Subir K. , Brown Susan L.
Published: December 2007

In order to develop good estimates on the heat content of a geothermal reservoir and its formation resistivities, and for various drilling and completion decisions one needs, an accurate estimate of the formation temperature. Previous methods to determine static temperature required long shut in periods. The static temperature obtained using the conventional Horner plots were lower than the true reservoir temperature. A quid and easy method has been developed to calculate static temperature from early shut in data in geothermal wells. This method determines static temperature values which are closer to the true reservoir temperature than those obtained from the conventional Horner plot. Recommendations for recording pertinent data to be used in the analysis of temperature buildup and determining initial reservoir temperatures are provided. Several examples are also given.
Radon Transect Analysis in Geothermal Reservoirs
Authors: Semprini Lewis , Kruger Paul
Published: December 2007

Radon transect experiments have been conducted to study flow and emanation characteristics of geothermal reservoirs. Transect experiments have been carried out at three geothermal reservoirs: 1) The vapor-dominated field at The Geysers, California; 2) the liquid-dominated field at Wairakei, New Zealand; and 3) the liquid-dominated field at Cerro Prieto, Mexico.

The radon transect technique involves an examination of the concentration gradients of radon and other natural components in the geofluid along a line of geothermal wells having structural significance in the reservoir. To obtain information on the flow regime in the reservoir, stable gas components in the geothermal fluid are measured in addition to radon. If the transport time of the fluid from the radon source to the wellhead is within a range comensurate with the 3.83-day half life of radon, variations in radon concentration along the transect relative to stable component concentrations provide temporal information on the flow regime.

Data from the transect experiments are being evaluated with mass transport models for vapor and liquid-dominated reservoirs. Results from The Geysers transect experiments show correlation between radon and stable gas components concentration gradients along structural features, indicating physical processes other than radioactive decay are governing radon concentration at the wellhead. Transect tests in the liquid-dominated reservoirs show correlation between radon concentration and fluid enthalpy, indicating the influence of two phase flow conditions in the reservoir. These initial results suggest that radon transect analysis may be useful in studying geothermal reservoirs. They should also help in the selection of wells for pressure transient and mass transient analysis, since it appears that wells in different areas of a large geothermal reservoir may be operating under different thermodynamic conditions.
The Role of Acidic, High Molecular Weight Crude Components in Enhanced Oil Recovery
Authors: Pasquarelli Carl H. , Brauer Paul R. , Wasan Darsh T. , Ciempil Michael , Perl Jeffery P.
Published: December 2007

Acidic resins naturally occurring in crude have been found to be responsible for a variety of interfacial phenomena in oil-aqueous systems. Those components which colloidally suspend high molecular weight asphaltene particles may also be used in enhanced recovery processes to inhibit asphaltene deposition in porous media. This paper presents results of laboratory core flooding tests using a microwave absorption technique to monitor in-situ oil/water saturations during enhanced recovery by alkaline flooding.

Resinous additives were found to significantly alter permeability reductions caused by asphaltene deposition and to affect the formation of a single and continuous oil bank during the laboratory core flood. Data were also obtained for the dynamic interfacial tension, electrophoretic mobility and emulsion stability for the whole crude/aqueous solution with and without the resinous additives.

These observations, combined with microwave analysis are used to suggest a possible mechanism for improved oil recovery through the prevention of asphaltene deposition and resulting permeability reductions.
Field Evaluation of Solids Control Equipment
Authors: Planck Jeffery W.
Published: December 2007

Programs for field evaluation of solids control equipment have been developed for a hand-held programmable calculator. The evaluation yields significant information using typical field equipment.

Such an analysis is useful for economic decisions at the wellsite, regarding a water-based drilling fluid, when equipment efficiency is a consideration. Such economic considerations as barite loss, expensive fluid phase loss, and actual cleaning efficiency of equipment (to determine if adjustments are needed) can be done in the field. The program is easily adjusted for brine systems and can be designed for a specific fluid on a specific well. Examples are included herein, as well as the formulas used (for a fresh water system) and wellsite testing procedures.

Program input data reflect density, rate, and component percentage. The output data yields total solids removed (in pounds per hour), average specific gravity of the solids, the percent and amount (in pounds per hour) of high and low gravity solids, and the amount of fluid lost (in barrels per hour).
An Engineering Economic Model for Thermal Recovery Methods
Authors: Williams R. L. , Ramey H. J. , Brown S. C. , Sanyal S. K. , Raghavan R.
Published: December 2007

An economic model for thermal recovery has been developed. This paper evaluates the optimum recovery rates and production schedule under both steam drive and in-situ combustion processes, possible future production, and the economics of each method based on today's prices.

The recovery model for steam injection is based on the work of Ramey and Raghavan1 which presented a computer program to determine surface steam line and wellbore heat losses, vertical heat losses to the adjacent formation, an oil recovery schedule, and associated steam injection calculations. The recovery model of in-situ combustion is based on the Gates and Ramey2 method of making engineering calculations of air-oil ratios and oil rates as a function of oil recovery.

Once recovery rates for steam drive and in-situ combustion are obtained, a cash flow analysis may be made. Capitalization and operating costs are considered and income is discounted to net present worth. Thus, an engineer may be able to use this method to help evaluate which processes would be more profitable for a particular reservoir.
Interpretation of Injection Well Pressure Transient Data in Thermal Oil Recovery
Authors: Satman Abdurrahman , Eggenschwiler Mauricio , Ramey Henry J.
Published: December 2007

A study was made of methods for burned volume, or steam swept volume, determination from pressure transient test data taken on injection wells. The basis for determination of the swept volume was a new pressure transient model of a composite reservoir. The swept volume was modeled as a radial region adjacent to the injection well, which was considered to have both wellbore storage and a skin effect. The permeability, porosity, and compressibility of the reservoir fluid were considered to be different in the inner region, representing the swept region, and the outer region, representing the bulk of the reservoir. The fluid flowing was considered to be of slight compressibility. The solution technique was analytical, using the Laplace transformation with numerical inversion. This solution has a wide application for problems other than detection of swept volume in thermal oil recovery. Superposition was used to generate the effect of a pressure injectivity test after growth of a swept volume. The results indicate a short duration wellbore storage effect, followed by a semilog straight line whose slope is related to the permeability/thickness of the swept volume. The semilog straight line is then followed by a pseudosteady Cartesian straight line characteristic of the swept volume. Finally, a second semilog straight line appears, characteristic of the permeability-thickness of the unswept region. The discovery of the pseudosteady portion seems to be a major finding. It is possible that this method can be used successfully to detect the swept volume connected with injection wells.

Another important finding is that the initial wellbore storage effect dies in a few minutes, and the semilog straight line characteristic of the swept volume occurs almost immediately on shut-in. Further, the pseudosteady period occurs in durations from a fraction of an hour to a few hours. The consequences of this kind of test in thermal recovery operations appear to be extremely important. Early detection of swept volume would mean rapid measurement of the fuel concentration for a combustion operation, and the heat loss from a steam zone! There has not yet been time to study all consequences of this new interpretation method, but it is fair to say that this kind of well testing offers operational information of the greatest importance.
The Coalbed Methane Resource of the Illinois Basin
Authors: Archer Paul L. , Carr Donald D. , Harper Denver
Published: December 2007

A program was initiated to determine the extent of the coalbed methane resource and the location of the most favorable resource areas within the Illinois basin, and to obtain a better understanding of the relationships between selected variables and the gas content of coals. Preliminary gas in-place resource estimates are made based on coal desorption data and the most favorable resource areas are outlined. Limited and/or poor data precluded establishing relationships between various geological-chemical/physical parameters and coal gas content. Further investigations are required to determine such relationships and to define what percentage of this resource is producible.
Developments in Well Completion Techniques
Authors: Coburn R.W.
Published: December 2007

Field experiments indicate that well stimulation efficiency can be increased by engineering the completion process as an interrelated series of steps. These steps can be selected in a manner tat will create conditions most conducive to successful stimulation. Revision of perforating procedure, and consideration of injection rate per hole as a basis for designing fracture treatments will aid in successfully completing wells at lower cost. Pressure behavior patterns can be translated into efficiency which in turn can be indicative of the effectiveness of the treatment.

Introduction

The method of treating wells to increase production has not changed greatly through the years. Acid, and most recently, fracture fluid, have been injected into the formation with no real attempt being made to engineer the treatment. Injection rates, volumes, and perforating procedures have been selected on past experience or "rule of thumb" type thinking. In an attempt to improve the effectiveness of well stimulation methods, several innovations have been employed. Perforating procedure has been revised to reduce the number of holes shot. This is accomplished by reducing perforation density (no. of holes/ft) and by being increasingly selective in the placement of the perforations. The use of a value called injection rate/hole as a primary factor in designing stimulation treatments has increased the effectiveness of these treatments. The analysis of pressure behavior during a treatment has revealed a method of recognizing the occurrence of communication behind the pipe. This in turn led to the development of a means of predicting the effectiveness of a treatment. This paper is concerned with the completion of wells which require stimulation to increase production. The methods described herein can be applied to any treatment which depends upon the injection of fluid into the formation.

Developments

There are three basic phases of well stimulation which have been revised as a result of successful field experiments. They are: hydraulic fracturing methods, perforating procedure, and the evaluation of the completion procedure. Taken individually, each is important; together, they represent a method of increasing the efficiency of present well completion techniques.

Fracturing

Since the inception of hydraulic fracturing as a means of increasing oil production, the oil industry has been constantly seeking to improve the techniques. The volume of treating fluids has risen, injection rates have climbed steadily upward, and blocking agents have been developed. The treatments were designed principally by rule of thumb or by past experience.
IN Situ Evaluation of Several Tailored-Pulse Well-Shooting Concepts
Authors: Schmidt Richard A. , Warpinski Norman R. , Cooper Paul W.
Published: December 2007

Dynamic stimulation techniques that produce multiple fracturing in a wellbore are being investigated for enhanced gas recovery. Multiple fracturing appears to be especially promising for stimulating naturally-fractured reservoirs, such as the Devonian shales, since this may be the most effective technique for connecting a wellbore to a pre-existing fracture network. Previous studies have demonstrated that detrimental effects can occur with high-strength explosive techniques and that these effects can be avoided through the use of propellants.1,2 The use of propellants and other so-called tailored-pulse techniques depend on a controlled pressure-time behavior to minimize wellbore damage and maximize fracture growth by gas penetration.

This paper describes a series of five full-scale tests performed to evaluate various multi-frac concepts. The tests were conducted at the Nevada Test Site in cased, horizontal boreholes drilled in ash-fall tuff from a tunnel under 430 m of overburden. This site provides both realistic in situ conditions for the tests and access to the stimulated regions by mineback which permits direct observation of results. The five tailored-pulse concepts tested involve:

Case A - a decoupled explosive,3 Case B - a decoupled explosive with propellant booster,3 Case C - a small-diameter propellant charge with pressurized water pad,4 Case D - three successive shots of Case C, and Case E - a full-diameter charge of a progressively-burning propellant.2

While direct observation by mineback is highly beneficial, evaluation and analysis of these test results also depended heavily on other diagnostics. Thirty-six stress-meters and accelerometers were fielded in the surrounding rock to record the dynamic disturbances, and each borehole contained transducers to measure the actual cavity pressures. Pre-test and post-test evaluations include TV log, caliper log, and permeability measurements. Permeability, which evaluates the effectiveness of the created fracture network to transmit fluids, was determined by analysis of constant-pressure, water-injection tests and the subsequent pressure decline after shut-in.

Results show a large increase in formation permeability for Case E, modest increases for Cases B, C, and D and a decrease for Case A that appears due to the formation of a stress cage. A comparison of Case E results with previous tests suggests a multiple fracture criterion based on pressure rate with little effect of peak pressures.
Empirical Evaluation of Clinton Sand Well Performance
Authors: Skillern Charles R.
Published: December 2007

The production economics of tight to near-tight formations such as the Clinton sands of Ohio have become increasingly marginal due to rapidly increasing well costs and geologically less favorable areas to drill. To evaluate the potential for improved well performance, the Gas Research Institute (GRI) sponsored the empirical investigation of historical Clinton sand well performance presented herein.

The study is based on well data from 303 wells in northeastern Ohio which were drilled between 1963 and 1974. All the wells were single-completions stimulated by hydraulic fracturing for which at least five years of uninterrupted production data are available. The data are believed to be representative of Clinton wells in the 1963 to 1974 time frame and were selected only on account of availability. Statistical regression methods were used to determine well parameters which impact individual well performance. The five-year cumulative production (first five years) for each of the 303 wells was used as the dependent variable in a multivariable linear regression equation, with the statistically significant well parameters as independent variables.

The empirical regression equation was used to estimate average well performance (five-year cumulative production) for geographically oriented subsets of the 303-well data base with varied levels of stimulation treatment volume. Significant variations in well performance are demonstrated as a function of apparent geologic variations and variations in stimulation treatment volume. Historical production (303 wells) could have been increased by 15 percent through use of near-optimum stimulation treatment volumes. A method is proposed which utilizes the statistical regression methods of the study, in conjunction with exploratory drilling in areas which are geologically similar to those represented by the data base, to assist in optimizing future Clinton sand production.
Development of Associative Polymer Technology for Acid Diversion in Sandstone and Carbonate Lithology
Authors: Eoff Larry , Dalrymple Dwyann , Reddy B. R.
Published: December 2007

This paper describes the use of associative polymer technology (APT) to achieve fluid diversion during an acid stimulation treatment. APT involves the use of a very low-viscosity aqueous polymer solution. It reacts immediately with the formation surface to significantly reduce the ability of subsequent aqueous fluids to flow into high-permeability portions of the rock. The first stage containing the APT predominately will enter the most permeable area, diverting following acid stage(s) to less permeable sections of the rock. APT has little or no effect on the flow of subsequent hydrocarbon production. Furthermore, in rock containing significant proportions of sandstone-type lithology, the water permeability of the treated zone is decreased permanently, resulting in post-treatment reduced water production from the treated zone.

This paper includes a general description of associating polymers and their properties, as well as a detailed description of the laboratory development of the current system. Laboratory data showing the ability of APT to reduce the ability of aqueous fluids to flow through porous media is presented. Parallel flow studies using water-saturated and oil-saturated cores are presented that show the ability of APT to divert acid in both sandstone and carbonate cores. These tests also show the ability of APT to decrease water permeability in the water-saturated core while the diverted acid increases the permeability of the oil-saturated core.
An Evaluation of the Geopressured Energy Resource of Louisiana and Texas
Authors: Samuels Garland
Published: December 2007

The economics of extracting either the geothermal energy or natural gas from geopressured aquifers does not look promising. The combined requirements of high well flow rates, long life, and the necessity for close well spacing to minimize the cost of the collection system may be incompatible with the actual characteristics of the reservoirs. These factors place such stringent requirements on the reservoir size, permeability and compressibility that the number of promising production areas may be severely limited.
Natural Gas from Tight Siltstones in the Catskill Clastic Wedge in West Virginia
Authors: Schwietering Joseph F.
Published: December 2007

Stratigraphic studies of Middle and Upper Devonian rocks in West Virginia suggest that thick zones of interbedded siltstone and shale present between the Devonian Shale gas fields in southwestern West Virginia, and the gas fields in Upper Devonian sandstones and siltstones in central and eastern West Virginia may contain important reserves of natural gas. Wells drilled into these zones of interbedded siltstone and shale should be completed in the same way as wells drilled into the black shales; i.e., the entire zone should be fractured, not selected siltstones.
Foam Fracturing: Theories, Procedures and Results
Authors: Gaydos J. S. , Harris P. C.
Published: December 2007

For the past several years, foam has been used in many treatments as a fracturing fluid. Although many different types of reservoirs have been stimulated with foam, the primary zones of interest in Eastern Kentucky and Southern West Virginia have been the Berea Sandstone and the Devonian Shales. Due to the nature of these formations, i.e. low permeability, low bottom-hole pressure and water sensitivity, foam fracturing has been a successful technique.

This paper presents the basic background theory of foam and presents several basic treatment designs which have been used successfully in the Devonian Shales and Berea Sandstone. Production histories for up to two years on a number of wells fractured with foam are compared to production histories of offset wells which were conventionally fractured with gelled water. In all the side-by-side comparisons, foam fracturing was found to give production results either as good as, or better than, conventional fracturing with gelled water.
Methane Recovery from Deep Unmineable Coal Seams
Authors: Allred Larry D. , Coates Ralph L.
Published: December 2007

Mountain Fuel Supply Company and the U. S. Department of Energy are conducting a joint project to demonstrate production and recovery of methane gas from deep coal seams in the Book Cliffs coal field of central Utah. The objective is to drill three wells to depths near 3000 feet to determine if commercial quantities of gas can be produced, and then to install production facilities for injecting the gas into the Mountain Fuel Supply gas transmission system.

Two of the three wells have been drilled and testing has been initiated. Five coal seams were encountered at depths between 2681 and 3112 feet. Core samples were obtained and desorption measurements indicate gas contents up to 400 cu ft/ton. The gas is approximately 95 percent methane. Water influx tests were made and water pumping equipment is being installed. Plans are being formulated to hydraulically stimulate the principal coal seams with nitrogen foam to increase production.
Methane Drainage from the Mary Lee Coalbed, Alabama, Using Horizontal Drilling Techniques
Authors: Perry John H. , Prosser Leonard J. , Cervik Joseph
Published: December 2007

The Bureau of Mines has developed several techniques for draining methane from coalbeds in advance of mining. Drilling long horizontal holes from an underground location is one of these techniques which has been successfully demonstrated in the Pittsburgh and Sunnyside coalbeds. A similar project was successfully conducted in the Mary Lee coalbed at Jim Walter Resources Inc., No. 4 mine. In a year about 1.13 million m3 (40 MMcf) of methane was recovered from the coalbed.
Water Injection Completion Philosophy in A Deepwater Subsea Environment Requiring Sand Control: A Case Study of 29 Injection Wells West Of Shetland.
Authors: Roy Alistair , Thrasher David , Twynam Allan , Wilson Allan
Published: December 2007

Water Injection completion selection in a deepwater subsea environment requiring sand control is currently an inexact science with lack of a proven track record for life of field solutions. The West of Shetlands (WoS) fields Foinaven, Schiehallion and Loyal have been on injection since 1997 and are starting to develop a substantial track record of injection performance. This case study will provide a performance comparison of the 2 main completion types installed to date, namely Cased and Perforated (C&P) and standalone Wire Wrap Screens (WWS), along with a subset of a three zone Smart well completed with premium sand screens. The comparison focuses on 4 main areas;

– Well Longevity – Completion Efficiency (skin) – Injection Conformance (Near Wellbore) – Performance of single and multi-zone injectors

The WWS screen performance is further subdivided by clean-up technique of which there are currently 5;

– Backflow Oil Based Mud (OBM) – Bullhead Oil Based Mud – Bullhead Water Based Mud after spotting Breaker – Toe Fracture using External Casing Packer – Displace OBM to Solids Free OBM and bullhead

A variety of data will be presented as part of the comparison including, PLT Data, MDT Data, PFO Results, Hall Plots, UCS Data. A simple set of criteria is presented to select when C&P or sand screens are viable completion solutions.
Production Strategy for Thin-Oil Columns in Saturated Reservoirs
Authors: Kabir C. S. , Agamini M. , Holguin R. A.
Published: December 2007

Maximizing oil recovery in thin and ultra-thin (< 30 ft) oil columns is a challenge because of coning or cresting of unwanted fluids, regardless of well orientation. Significant oil is left behind above the well completion even for horizontal wells when bottom-or edge-water invasion occurs.

Two depletion strategies may be enacted to improve recovery of the remaining oil. In the first option, a conventional horizontal is completed below the gas/oil contact (GOC). Once the well waters out, the well is recompleted in the gas zone. Completion occurs either at the crest for a small gas-cap reservoir or at the GOC, inducing reverse cone, for reservoirs with thick-gas columns. Alternatively, one can skip the initial oil completion. Gravity-stable flooding is required to maximize reserves.

Extensive flow simulations in multiple, history-matched models have shown that the proposed strategy improves recovery significantly. Two field examples are presented to demonstrate the usefulness of the proposed method.

Using multivariate regression, simple correlations were developed for quick screening of the proposed approach. Experimental design formed the backbone of a parametric study involving various reservoir, fluid, and process variables. We tested and validated the correlations with independent sets of experimental and published field data.
Log Reprocessing: Petrophysical Lessons from the Giant Oil and Gas Fields of Saudi Arabia
Authors: Kersey David G. , Al-Ali Hussein A. , Eyvazzadeh Ramsin Y. , Phillips Craig , Tjan Tjwan L.
Published: December 2007

Results from Saudi Aramco's log reprocessing project provide guidelines for reprocessing fields of all sizes. The database included openhole logs from 8,700 wells acquired over almost seventy years by three contractors using various generations of tools. The main goal was to develop a functional, accurate and accessible log data base of both quality-controlled raw logs and uniformly processed, core-calibrated interpretation logs. The project was divided into five phases: log editing, core/log integration, normalization, petrophysical processing and archiving.
Analysis of an Annular Pressure Buildup Failure during Drill Ahead
Authors: Pattillo P. D. , Cocales B. W. , Morey S. C.
Published: December 2007

While drilling ahead in salt on the Pompano A-31 (Gulf of Mexico) wellbore below the 16 in. shoe, the rotary stalled abruptly and the drill pipe simultaneously became stuck. Subsequent calipers indicated the 16 in. casing to be deformed onto the drill pipe at approximately 250 ft.

To the authors' knowledge, this represents the first instance of an annular pressure buildup (APB) failure during drilling. APB is typically associated with extremes of temperature change resulting from production operations. In the current instance, the temperature change was solely from circulating drilling fluid.

The manuscript provides a detailed post-analysis of the 16 in. casing failure:

An overview of the conventional casing design for this well, indicating that normal operating conditions should not have resulted in a failure; A review of the failure event, substantiated by field measurement and photographs; An investigation of APB associated with inadvertently closing the 16 in. casing annulus at the surface, demonstrating the magnitude of thermally induced pressure load that can result; Consideration of an alternate failure mode, column buckling, to demonstrate that this failure mode was not active in this wellbore; A finite element model of the drill pipe/16 in. casing/20 in. casing trio indicating that, in addition to collapse of the 16 in. casing and subsequent sticking of the drill string, the outer 20 in. casing was also damaged by the event.

The latter item is particularly important in that damage to outer strings can be easily overlooked as one concentrates on the collapsed casing and drill pipe fish. Damage to the outer 20 in. string is confirmed by a mechanical caliper.

Conclusions in the paper center on confirmation of the postulated failure mode by field measurement and recommendations for avoiding such an event.
Using Multifrequency Sonic Velocities for Geomechanics Applications
Authors: Lacy Lewis L. , Jiao Di
Published: December 2007

A relatively new method has been developed and tested to determine compressional and shear wave velocities and quality factors versus frequency for reservoir rock under a wide variety of reservoir conditions. This new method depends on measuring the Dynamic Elastic Moduli (DEM) at multi-frequencies. The reasons for performing multi-frequency measurements are reviewed in the paper along with potential reservoir applications used in petroleum engineering, geophysics and dipole sonic log calibrations. Typical data are reviewed using pure aluminum for calibration and investigating the method using both Berea sandstone and reservoir sandstone at different saturation conditions.
Integration of Streamline Simulation and Automatic History Matching
Authors: Maschio Célio , Schiozer Denis J.
Published: December 2007

This paper presents an integration of different methodologies for history matching of complex fields. For such cases, a fine grid model is necessary and, therefore, the simulation time is high, yielding a constraining factor because the number of simulations must be limited in such cases in order to turn the process feasible. The proposed approach combines three fundamental steps: (1) a global history match; (2) the use of streamline simulation to determine flow path among producers and injectors or between an aquifer and a producer well to facilitate the choice of regions of interest to history match individual wells; and (3) the history match of wells through the modification of the properties of the regions of interest. The first and third steps are performed using an automated history matching methodology, which uses parallel computing and traditional simulation procedure.

The proposed approach is applied to a real case from an offshore field with 34 producer wells and 13 injector wells and a period of 22 years of production is available. Results showing the advantages and disadvantages of using an automated history matching in a complex field are presented. The use of streamline simulation as a support tool in such complex field history matching is also presented. Other aspects such as speedup of the process, using parallel computing, and high reduction rate of objective-function, by choosing correct regions for modification of the properties, are described in the paper.

The main contribution of this paper is to show a convenient form of combining two important tools: streamline simulation and automatic history matching of complex fields.
Field Experiences with Assisted and Automatic History Matching Using Streamline Models
Authors: Cheng Hao , Wen Xian-Huan , Milliken William J. , Datta-Gupta Akhil
Published: December 2007

Reconciling high-resolution geologic models to production history is a very time-consuming process in reservoir modeling. Current practice still involves a tedious historymatching process that is highly subjective and often employs ad-hoc property multipliers. Recently streamline models have shown significant promise in improving the history matching process. In particular, the streamline-based "assisted historymatching" utilizes the streamline trajectories to identify and limit changes only to the regions contributing to the well production history. It is now a well-established procedure and has been applied successfully to numerous field cases.

In this paper, we enhance the streamline-based assisted history matching in two important aspects that can significantly improve its efficiency and effectiveness. First, we utilize streamline-derived analytic sensitivities to determine the spatial distribution and magnitude of the changes needed to improve the history match. Second, we use a "generalized travel time inversion (GTTI)" for model updating via an iterative minimization procedure. Using this approach, we can account for the full coupling of the streamlines rather than changing individual or bundles of streamlines at a time. The approach is more akin to automatic history matching. However, by intervening at every step in the iterative model updating, we can retain control over the process as in assisted history matching. Our approach leads to significant savings in time and manpower during field-scale history matching.

We demonstrate the power of our method using two field examples with model sizes ranging from 105 to 106 grid blocks and with over one hundred wells. The reservoir models include faults, aquifer support and several horizontal/high angle wells. History matching is performed using both assisted history matching and the GTTI. Whereas the general trends in permeability changes are similar for both the methods, the GTTI seems to significantly improve the water cut history matching on a well-by-well basis within a few iterations. Our experience indicates that the GTTI can also be used very effectively to improve the quality of history match derived from the assisted history matching. The changes to the reservoir model from GTTI are found reasonable with no artificial discontinuities or apparent loss of geologic realism.
The Effect of Oil Brine Ratio on Surfactant Adsorption From Microemulsions
Authors: Meyers Kevin O. , Salter Stephen J.
Published: December 2007

Static adsorption measurements of petroleum sulfonates on crushed Bell Creek and Berea cores were made utilizing fluids with the same active surfactant concentration but varying brine-to-oil mass ratios. The salinity of the brine was chosen such that a significant three-phase region existed in the oil/brine/surfactant/alcohol system. The surfactant adsorption was found to be independent of the structural and compositional differences among the fluids.

A series of oil recovery tests in which middle-phase microemulsions were injected into waterflooded cores were also carried out. The cores utilized in these tests had been treated to remove divalent ions accessible to fluid flow. Microemulsion slugs (1.75 to 146 percent pore volume) of equal active surfactant concentration but differing brine-to-oil mass ratios were injected. The total surfactant retention for this system was also found to be independent of the brine-to-oil mass ratio.
Purification of Coal-Bed Methane Produced Water by Zeolite Membranes
Authors: Liangxiong Li , Ryan Ashlee , Nenoff Tina M. , Dong Junhang , Lee Robert
Published: December 2007

This paper reports a new method for purification of coal-bed methane (CBM) produced water by reverse osmosis (RO) through molecular sieve MFI zeolite membranes. The desalination on the zeolite membrane can be thought of as an ion sieving process — the uniform zeolitic pore size (dia. ~0.56nm for MFI) is sufficient for transport of water molecules (dynamic size ~0.29nm) but is small enough to reject hydrated ions and large organic molecules by size exclusion.

In this study, the MFI zeolite membranes were used for desalinating a CBM produced water from Farmington, NM, which contained total dissolved salts (TDS) of ~1.86×104 ppm. The effect of dissolved organics on the desalination efficiency was examined by comparing RO performance for 0.10M KCl solutions with and without dissolved toluene, which was used as a simulator of dissolved organics. The zeolite membrane showed an overall salt rejection of 83.5% for the CBM produced water with organics removed by pretreatment. Experimental results also show that the dissolved toluene affected the ion rejection and water flux only slightly. Due to its extraordinary chemical and structural stabilities, the MFI zeolite membrane may offer an alternative method to treat the organic-containing, high TDS CBM produced water for beneficial use.
Sanding: A Rigorous Examination of the Interplay between Drawdown, Depletion, Start-up Frequency and Water Cut
Authors: Vaziri Hans , Allam Robbie , Kidd Gordon , Bennett Clive , Grose Trevor , Robinson Peter , Malyn Jeremy
Published: December 2007

Factors and mechanisms leading to sanding are described within an integrated rock and soil mechanics framework. While the conventional sanding models generally consider a single-mechanism for sanding, namely the critical depletion resulting in rock disaggregation, the proposed approach considers the inter-play of several mechanisms that can lead to the rock break-up and sand transport. One important difference is that rock disaggregation is not seen to represent the onset of sanding as the sand mass can offer significant resistance due to frictional properties, interlocking of sand grains and arching. The approach presented can be used to explain why sanding in the field tends to be episodic and how depletion, which is a major factor in rock break-up, can be highly effective in holding broken up sand grains together and become a sand stabilization agent.

The proposed approach is used in discussing sanding at several wells in two different fields. These wells have been in production for several years and show that sanding cannot be linked to just one unique mechanism (e.g., depletion). However, once all mechanisms for sanding are incorporated, a more consistent analysis can be used by completion and production engineers to make more objective and pragmatic decisions in managing sanding while maximizing production over the life of the well.
Integrative Interpretation of 3D VSP and Multisource Salt Proximity at Vinton Dome, Louisiana, USA
Authors: Li Yingping , Wang Dapeng , Jackson James
Published: December 2007

This paper presents 3D VSP imaging results of a salt-sediment boundary in the Vinton Dome Field, Louisiana, USA, using both borehole seismic reflection and refraction methods. The SS salt reflections were migrated to generate the salt-sediment boundary image volume and the PP sediment reflected waves were used to produce the depth migration image volume for the complex sediment structures. Multisource 3D salt proximity surveys result in 3D salt exit points which delineate the steep salt-sediment boundary with a significant overhang. 3D VSP Images from two methods are consistence, providing a greater degree of confidence in the interpretation of the complex 3D salt-sediment structures.

A 3D visualization tool especially designed for 3D VSP solutions was used to integrative interpret multi-volumes of 3D VSP images, salt exit points, velocity models, well logs, surface seismic data, and other available data. The use of multifarious VSP imaging techniques and 3D visual tool provides validation of the various results and yields an accurate picture of the salt flank position.