bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reservoir Properties Required for Profitable Stimulations
Authors: Dietzel H. J. , Ernst P. L. 
Published: December 2007

Abstract
Profitability of production from low permeability gas reservoirs is mainly determined by the increment of production obtainable by hydraulic fracturing as well as by the initial flow capacity of the untreated well.
In this paper a method is presented, which allows a judgement of profitability of low permeability gas production on the basis of log-analysis and well-testing data only.
Deduced from reservoir models production profiles for an untreated and a fractured well, respectively, are calculated. To these production profiles basic profitability analysis are applied, considering –drilling and completion costs–surface treatment installations–MHF-treatment charges
The limiting value of profitability is characterized by a dcf-rate of 15 %.
On the basis of economic considerations, limiting values for reservoir properties are determined as requirements for a profitable stimulated or non-stimulated production from low permeability gas reservoirs.
Polymer Emulsion: The Revival of a Fracturing Fluid
Authors: Roodhart L. P. , Davies D. R. 
Published: December 2007

ABSTRACT
Polymer emulsion hydraulic fracturing fluids were widely employed some 10 to 15 years ago, but became less popular after the introduction of cross-linked, water-based gel systems. The latter were thought to have a higher viscosity and be easier to handle, as well as being cheaper. However, during the last few years, polymer emulsions have enjoyed an increasing popularity in Europe because of their flexible viscosity response and their non-damaging properties1. In addition, their cost per unit volume of proppant placed is now comparable to that of water-based fluids.
Addition of a well-dispersed internal phase will increase the viscosity of any fluid over that of the external phase alone. For polymer emulsion fracturing fluids the continuous phase is gelled water, the viscosity being enhanced by the addition of diesel, kerosene or crude oil at typical volume fractions between 0.5 and 0.7. During the proppant stage, the fluid rheology is further complicated by the addition of a second internal phase (sand) to the emulsion, which will not only increase the viscosity, but will also affect the stability of the emulsion if the total internal phase (sand + oil) exceeds a maximum value. However, the existence of two different internal phases offers the possibility of gearing the volume fractions of two alternate phases to each other in such a way that the slurry viscosity is constant and independent of the sand concentration. This is particularly important in situations where the tubing head pressure is limited and tubing friction becomes critical and cannot be allowed to increase as the sand concentration is increased during the job.
A last, but not the least, parameter affecting the emulsion rheology is the amount of shear applied to the emulsion while generating it. It was noticed that emulsions prepared in the field had a lower viscosity than emulsions prepared in the laboratory. This difference could be attributed to a different oil droplet size distribution in field- and laboratory-prepared samples. The efficiency of the equipment used in the field to generate an emulsion lags behind that of laboratory equipment, especially at high oil/water ratios and high gel loadings. This is an area where further improvements can be made by the service companies.
Polymer emulsion frac. fluids are thus attractive because of the wide span of control available to the operator.
Field data (THP and BHP data) proved that these rheological correlations effectively described the situation in the field, the predictive accuracy of the formulae being such that the fracture shape may be evaluated from THP data.
Some 25 fracturing treatments have been carried out in Europe using polymer emulsion fracturing fluid with a very high success ratio. Productivity improvement factors of nearly 30 were achieved with few operational problems using sand concentrations up to 14 lb/U.S. gal.
Hydraulic Fracture Treatment Design Simulation for the Rotliegendes Formation
Authors: Acharya A. , Kim C. M. 
Published: December 2007

ABSTRACT
As an increasing number of gas fields are being developed or are planned to be developed in the permian red beds (Rotliegendes) of northwest Europe, hydraulic fracturing has become a major stimulation method to obtain economic production rates from this tight gas formation. Optimization of stimulation design and its implementation in the field become more crucial in the formation such as Rotliegendes, where a water bearing zone is underlain. The objective of this work was to simulate fracture growth under various conditions so that optimal treatments can be designed and implemented successfully to this tight gas reservoir. Formation rock properties of the payzone and adjoining barriers, fracturing fluid properties and their leakoff coefficients selected were experimentally determined in the laboratory using various Rotliegendes core samples. A 3-D model of Meyer and Associates was used to simulate the fracture length, width, height, proppant transport and settlement, fracture closure, and post-frac performance. The same treatment data were simulated using a 3-D model developed by Palmer and Carroll. Results obtained from the two models are compared on a rational basis.
Two field applications are presented to demonstrate the proper design and successful stimulation treatments in the Rotliegendes.
Source Rock Evaluation: A Method of Predicting Dominant Reservoir Mechanisms of Deeply Buried, Low-Permeability Coal Reservoirs
Authors: Decker A. D. , Horner D. M. 
Published: December 2007

ABSTRACT
The ability to produce low cost, pipeline quality gas from low permeability deep coal reservoirs depends largely on thorough integration of exploration methods with appropriate drilling, completion and production strategies. In the extreme case, areas that are not economic with current completion technologies should be avoided with adherence to prudent exploration practices. Therefore, reliable predictive geologic methods to specify coal reservoir conditions need to precede drilling and completion decisions.
Dominant coal reservoir mechanisms include: permeability, saturation, reservoir pressure and gas-in-place. Production characteristics from low permeability coal reservoirs are most sensitive to the interaction between type of saturation and reservoir pressure. The geologic processes responsible for these reservoir conditions have been examined in the Piceance Basin. This basin, known for low permeability reservoirs, was selected for geologic evaluation due to the large coalbed methane resource and large data base. Also located in the basin is the Deep Coal Seam Project, a multiyear, multi-well, field laboratory joint venture by the Gas Research Institute and Resource Enterprises, Inc., providing fully integrated reservoir and geologic engineering data on deep coal reservoirs.
Reservoir diagnostics and modeling suggests that reservoir pressure and type of saturation demonstrate an interaction between catagenesis and permeability. Thick, thermally mature coal deposits actively generate more gas than can be adsorbed by the coal or be diffused through a low permeability system. In these regions over-pressuring occurs. Ultimately, pore pressure will exceed in-situ stresses resulting in tensional fractures through the coal bearing sequences. While the coal seams remain in the active gas generation phase, the fractures and pore spaces become gas saturated. Eventual temperature reduction through erosion will halt the gas generating phase, resulting in an under-pressured reservoir. Imbibition of water into these reservoirs is unlikely in areas of low permeability.
In summary, source rock evaluation techniques have been applied to characterize and predict coal reservoir mechanisms in low permeability basins.
The Use of Simulation and History Matching To Determine Critical Coalbed Methane Reservoir Properties
Authors: Zuber M. D. , Sawyer W. K. , Schraufnagel R. A. , Kuuskraa V. A. 
Published: December 2007

ABSTRACT
Key coalbed methane reservoir properties can be determined using a logical history matching analysis procedure that incorporates laboratory, geologic and production data. Methane and water production data were history matched using a dual-porosity, two-phase finite difference reservoir simulator modified to account for the storage and flow mechanisms unique to coal. Two field examples demonstrate the results and show the applicability of reservoir modeling to assessing the effectiveness of stimulation and predicting well performance.
The Analysis of Complex Travis Peak Reservoirs in East Texas
Authors: Holditch S. A. , Robinson B. M. , Whitehead W. S. 
Published: December 2007

ABSTRACT
In order to evaluate the effectiveness of a hydraulic fracture treatment, one must be able to correctly analyze post-fracture production and pressure buildup data. In many cases, conventional analysis techniques or simple single-phase, two-dimensional models are all that is required to obtain satisfactory results. However, in complex reservoir systems, such simplified techniques may provide incorrect solutions. As part of a research program sponsored by the Gas Research Institute (GRI) a substantial engineering effort is being exerted towards better understanding of complex reservoir systems. The thrust of this work has been in the Travis Peak formation of east Texas which is a multi-layered reservoir that normally produces both gas and water. To properly analyze this formation, a three-dimensional and/or two-phase reservoir simulator is needed.
This paper presents a thorough discussion of the problems associated with the analysis of complex reservoirs and illustrates these problems with numerous field examples. Examples are included in which short, high conductivity fractures are calculated when conventional analysis techniques are used. However, a longer, more realistic estimate of fracture length is computed when one uses a multi-phase, multi-dimensional reservoir model to accurately history match the gas and water flow rates as well as the wellbore pressures.
An Equivalent Cell Block Porosity and Permeability Concept for Modeling Multiphase Flow in Naturally Fractured, Lenticular Reservoirs
Authors: Evans R. D. , Ubani E. A. 
Published: December 2007

ABSTRACT
A mathematical model is presented which forms the basis of a multiphase, three dimensional reservoir simulator for characterizing multiphase flow in naturally fractured, lenticular formations. The model is general in that it can treat the presence or absence of natural fractures and/or sand lenses in a statistical fashion based upon a known distribution for each. A double porosity medium is approximated by an equivalent single porosity medium for each cell block. Similarly an equivalent permeability for each cell block is approximated by calculating an effective principal permeability as a function of rock matrix and fracture permeabilities. In any given cell block the fractures can have any orientation. The model can be used to simulate the behavior of a double porosity medium composed of heterogeneous, anisotropic rock matrix, and a heterogeneous, anisotropic fracture system. In addition it possesses the capability of including sand lense lenticularity and hydraulically created fractures with finite or infinite conductivity. Simulation results are presented for an actual field case and for hypothetical wells producing under multiphase flow conditions.
Coupling of Production Forecasting, Fracture Geometry Requirements and Treatment Scheduling in the Optimum Hydraulic Fracture Design
Authors: Meng H. Z. , Brown K. E. 
Published: December 2007

ABSTRACT
There are a number of considerations to be made in the process of designing a fracturing stimulation treatment. The reservoir deliverability, well producing systems, fracture mechanics, fracturing fluid characteristics, proppant transport mechanism, operational constraints and economics should be considered and integrated in order to obtain the most cost-effective design and to maximize the benefit of a well stimulation treatment.
The main purpose of this work is to develop an analytical scheme which mathematically couples each elements as described above. The criteria used to determine the optimum size of the treatment are: (1) optimize reservoir deliverability, (2) maximize propped fracture penetration, (3) optimize pumping parameters, (4) minimize treatment cost, and (5) maximize economic returns of the well.
Firstly, an analytical inverse algorithm has been derived based on 2-D PKNC (Perkins, Kern, Nordgren and Carter) and KZGD (Khristianovic, Zheltov, Geertsma and de Klerk) formulations. It allows us to calculate the fluid and proppant volume needed for a desired fracture geometry and conductivity. Secondly, a technique to search for optimal pumping parameters and to maximize the proppant coverage for a given hydraulic penetration is developed. This allows us to optimize the propped geometry taking into account the operational constraints. Thirdly, a coupling algorithm is developed to link the reservoir producibility, well producing systems and the optimized fracture geometry. This enables us to optimize the wellhead deliverability based on the balance between the reservoir and the fracture characteristics. Finally, the overall economic analysis is performed to calculate the net present value for various design options. The most cost-effective treatment design can then be determined based on the point of diminishing return on the well's net present value.
Realistic Fracture Conductivities of Proppants as a Function of Reservoir Temperature
Authors: McDaniel B. W. 
Published: December 2007

ABSTRACT
The steady-state conductivity of a propped fracture is significantly lower than has been reported in most of the data presently being used in fracture design calculations. When laboratory testing incorporates realistic parameters for temperature, and the tests are held for extended time periods, measured conductivity may only be a fraction of the previously reported value. Several authors have addressed this concern, each citing a very limited quantity of data. In some cases, only a few proppants were tested, while other authors addressed only one or two specific temperatures.
This work is based on the results of more than one hundred tests where each stress level was held for extended times to create a complete family of data for a representative number of proppants. The data covers a formation temperature range of 70° to 325°F and a stress range of 2,000 to 13,000 psi for several of the most commonly used proppants. The data were then incorporated into various computerized frac design simulation programs and in reservoir production simulation models.
GASWAT-PC: A Microcomputer Program for Gas Material Balance With Water Influx
Authors: Wang B. , Teasdale T. S. 
Published: December 2007

ABSTRACT
GASWAT-PC is a microcomputer material balance program that calculates original gas in place (OGIP) from production history for gas reservoirs with or without water influx. Several well-known analytical techniques, and some extensions and improvements, are applied to a single input data set. The output for each method is given in both tabular and graphical form.
GASWAT-PC also has the capability to predict reservoir pressure and recovery efficiency for a specified production rate if OGIP and aquifer properties are known. An option is included to account for the effect of a large pressure gradient in the water-invaded region.
Case studies illustrate the application of GASWAT-PC to an abnormally pressured reservoir and to two water drive reservoirs. Finally, we compare the pressure performance predicted by a numerical simulator and by GASWAT-PC for a water drive reservoir with a high dip.
Optimized PC-Based Expert Systems
Authors: Zamora M. , Merchant M. A. 
Published: December 2007

Abstract
Expert-system technology has emerged from beneath the umbrella of Artificial Intelligence and into the mainstream of engineering problem solving. There already are several notable examples of the application of this state-of-the-art technology in the petroleum industry.
Clearly, expert systems that run efficiently on standard personal computers are particularly of value. A new expert-system generator that overcomes the speed, memory and mass-storage limitations of XT/AT-class personal computers is presented in this paper. The shell is optimized for the specific characteristics of the target user, knowledge expert and computer. Expert systems developed using this shell currently are being used by our technical personnel for drilling fluid and related applications.
A New Two-Dimensional Single-Phase Waterflood Model for Microcomputers
Authors: Rezaei A. A. , Donaldson E. C. 
Published: December 2007

ABSTRACT
In the performance evaluation of any reservoir, a knowledge of the pattern of fluid flow within the reservoir is essential. This is especially true in the case of reservoirs under waterflood, where an analysis of injected fluid migration within the porous medium is very important. Hence, reservoir simulation has become a valuable tool for reservoir engineers, allowing them to gain greater insight into fluid flow within the reservoir. If properly conducted, a simulation study can aid in optimizing depletion by answering many specific questions related to a given reservoir.
This paper describes a single phase, two-dimensional, compressible front tracking model for microcomputers, which can be used to simulate waterfloods. It can be used for any type of heterogeneous reservoir with variable thickness, permeability, porosity and flow boundaries.
A complete discussion of the mathematical model, operating logic of the program, and sensitivity to input data is provided. Also, a listing of the program in FORTRAN is included. Anyone with access to a microcomputer can use the program to analyze the anticipated pattern of injected fluid migration within the reservoir as a function of time.
Applications of a Microcomputer Facilities Network Modeling Program
Authors: Startzman R. A. , Barnes G. A. , Wong S. A. 
Published: December 2007

ABSTRACT
This paper presents a system modeling program, designed for use on a microcomputer, which calculates steady-state pressures and flowrates for a single-phase gas or water system. The program can model flow through 1) well completions using IPR formulas; 2) flow lines (inclined, vertical, or horizontal); 3) fixed orifice chokes; 4) and single- or multi-stage reciprocating compressors. The program uses nodes to identify pressures and node connecting elements to identify flowrates and determine which type of element that is being modeled.
The program determines unknown pressures by either sequential or simultaneous methods. In the sequential method the program analyzes each node connecting element individually. The simultaneous solution creates a matrix containing flow balance equations from each node in the system. Next, the program solves this matrix simultaneously to determine values for the unknown pressures and flowrates. The purpose of this paper is to explain the logic of the modeling program and demonstrate its applicability in a microcomputer environment using examples.
Measurement-While-Drilling Tool Performance in the North Sea
Authors: Knox David J. W. , Milne John M. 
Published: December 2007

Abstract
The in-hole failure rate and survey accuracy are key areas when judging the performance of Measurement While Drilling (MWD) tools. Shell UK Exploration and Production (Shell Expro) extensive use of two major MWD companies has enabled the underlying trends to be identified.
The mean time between the failure rates of both directional-only and directional plus Gamma Ray tools, is presented by year from 1981 until April, 1987. Over this period, the mean time between failure (MTBF) of directional-only tools has risen from 225 hrs in 1981 to 360 hrs in 1986 with an average of 260 in-hole circulating hours between failures over the 6.3 year period. The average MTBF rate for Gamma Ray tools for 1983 until the end of 1986 is 160 hrs.
Survey accuracy has been established by comparing the horizontal difference between the 13 3/8 inch casing shoe position calculated from the MWD surveys and the positions measured by the Ferranti FINDS survey tool. 125 wells were analysed; 95% of these wells exhibit errors of less than 7, 9, 12, and 14 ft/1,000 ft of along hole depth surveyed for averaged inclinations of 0 – 15, 15 – 25, 25 – 35, 35 – 50 degrees respectively.
The data does not reveal any strong trend towards lower accuracy in East/West wells, but does indicate that magnetic disturbance is a major error source.
A History of Downhole Scale Inhibition by Squeeze Treatments on the Murchison Platform
Authors: Payne G E 
Published: December 2007

ABSTRACT
The formation water of the Murchison reservoir has a natural scaling potential. As pressure reduces from reservoir conditions carbonate scaling can occur. Also the water has a barium and strontium content so that when injected seawater broke through to the producing wells sulphate scaling also became possible. Initial scale inhibitor squeeze treatments achieved what scale itself to that date had not. They plugged the wells. Since then scale inhibitor squeezes have been successfully carried out and regularly achieve squeeze lives of up to a year.
This paper outlines in historical form the philosophies and events of downhole scale inhibition for the Murchison wells. The initial difficulties and present successes are described. Details are also given of previous problem areas of downhole asphaltene deposition and present thoughts on squeeze treating different producing zones within the same wellbore.
Thermite Sparking in the Offshore Environment
Authors: Hay E. , Adermann R. 
Published: December 2007

ABSTRACT
In flammable and explosive environments, sparks have to be eliminated for reliable operation and safety. Thermite sparking is a comparatively rare phenomenon which produces a relatively hotter spark than friction sparking. It involves aluminum alloys and rusted steel. This paper reviews and compares the mechanism of generating thermal and friction sparks and assesses the risks from thermite sparking. Various methods which can abolish this hazard are illustrated. The work reflects the findings of 200 publications.
The methods of thermite spark suppression in this paper will apply to all aluminum structures in drilling and production platforms. Such information will enhance safety in the use of aluminum alloys clarifying doubts about their use in the offshore environment. The paper will assess what precautions may be taken in the increasing use of aluminum on offshore structures.
Offshore Platform Removal and Abandonment 1987 – Review and Update
Authors: Boyd N. G. 
Published: December 2007

ABSTRACT
The publishing of the UK Government's "Petroleum Bill" has generated much interest and controversy in the subject of Removal and Abandonment of offshore installations; it is therefore particularly timely to review all the influences that may affect the situation and update the position for 1987.
It has now become apparent that there are many bodies, governments and other factors that may generate an impact on Removal and Abandonment and this paper starts with a brief outline of the situation in 1986. New influencing factors are then introduced and reviewed and the likely impact of these influences assessed. The paper concentrates on the UK sector but all the various influencing factors are equally relevant to the whole of the North Sea.