bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Low Density Tracers to Evaluate Acid Treatment Diversion
Authors: Reid Mark , Holcomb David , Waak Kyle A.
Published: December 2007

Utilizing a newly developed low density zero wash tracer carrier (1.1 - 1.5 gm/cc), acidizing treatments performed across large gross intervals consisting of thinly laminated carbonate/sandstone reservoirs have been more accurately diagnosed with respect to placement efficiency. Multi-isotope tracer in combination with spectral gamma ray logs are used to evaluate and optimize acid treatments involving various diverting processes (i.e., rock salt/benzoic acid; ball sealers). Acid diverter treatments are evaluated using multi-tracer spectral gamma ray logs and subsequent efficiencies shown. A new low density tracer carrier that allows more effective, safer transport and placement of the isotopes was used and significantly improved the log interpretation. Example case histories of acid treatments evaluated using the new low density tracer carrier will be presented for treatments done in Utah, U.S.A.

Acid treatments performed in long multi-perforated intervals using various diverting techniques were shown to have different coverage distribution than expected or indicated by treatment pressures. A new low density tracer carrier provides a clearer log definition where multi-isotopes are used to define acid stage and diverter stage distribution.

Applications

Acid treatment diversion efficiency and effectiveness can be more accurately diagnosed with the new low density solid isotope carrier instead of previously used highly adsorptive liquid tracers. Actual treatment placement can be more specifically defined without problems caused by wellbore contamination using liquid tracers. Log definition was improved as well by using the new low density solid, as opposed to liquid tracers.

A new tracer carrier to allow improved evaluation of acid treatment placement using diverters has been used and demonstrated to be more reliable than other solid or liquid carriers.

A low density, specially sized, ceramic material was developed and used to contain multi-isotopes: Ir-192, Sc-46, and Sb-124, so they could be transported more easily in acid treatments to evaluate both stage and diverter placement efficiency. This carrier helps eliminate loss of isotope to tubular surfaces.
Testing And Practically Applying Pump-Off Controllers In A Waterflood
Authors: Eckel Andy C. , Abels Harold P. , Merritt Ross A.
Published: December 2007

During the course of this study, many lessons have been learned regarding the practical, efficient use of pump-off controllers. Most were the result of effective field testing and effective communication with lease operators.

The purpose of this paper is to share the learnings about pilot testing, well selection, equipment selection and lease operator buy-in. By sharing these learnings, the authors hope to ensure that future applications of pump-off controllers are practically planned and efficiently installed - thus maximizing their economic potential.

Numerous papers have espoused the economic benefits of pump-off controllers. Most of the results and recommendations provided herein are qualitative in nature. Quantitative results are provided where applicable.
A Unique Method of Evaluating Stimulation Effectiveness in Production Damaged Slotted Liners
Authors: Wood William D. , McKeon Dan
Published: December 2007

After years of service in steamflood and cyclically steamed reservoirs, slotted liners tend to become clogged with migrating formation material and heavy asphaltene deposits1. These deposits seriously restrict inflow and typically make the wells economically unproductive. Acid wash jobs performed through coiled tubing jet wash tools have been found to be extremely effective as a damage removal technique. This paper describes development, testing and preliminary findings of a test vessel which can mechanically isolate small sections of damaged slotted liners and evaluate the effectiveness of different stimulation scenarios.
Hydratable Shales and the Salinity High Enigma
Authors: Overton Harold L. , Zanier Aldo M.
Published: December 2007

Water salinity in marine formations is shown to be a result of compaction and diffusion in the earth. Overpressure, rock stress and salinity variations are all related to drilling depth and geologic time by equations of the following type.

c'(-P) 2c = c 10 + AD sin (Z)(1-e- Dt).W Wo c

The constants A and are determined by boundary conditions and cWo and c' are related to geologic time. Zc is the depth below critical compaction. Whenever the age of a section is known, all of the parameters may be determined from a single well log. When a salt source is not present, the second term disappears or is supplanted by a sink term.

The deep drilling environment is dominated by the compaction and diffusion mechanisms. The occurrence of gas and condensate is predominantly a result of the salinity contrasts shown by these mechanisms, whenever mechanical trapping is present. The phase behavior of shales and their connate phase behavior of shales and their connate fluids, as well as hydrocarbon fluids, is related to the compaction and diffusion phenomena. phenomena

Introduction

The salinity principle has shown that rock stress, hydraulic pressure and the NaCl content of formation waters are macroscopically related. Whenever compaction stress reduces the water fraction of shales, the water in equilibrium between sands and shales becomes more concentrated. This happens consistently in areas with large shale fractions (greater than 50 percent), down to about 10,000-ft depth. The profile of salinity vs depth is very uniform in profile of salinity vs depth is very uniform in areas such as the Gulf Coast, so long as overburden is the dominant variable in the Tertiary. The gradient is of such reliability that the geologic age of the rock column between 3,000 to 8,000 ft can be determined about 75 percent of the time, using the following equation;

-10 558c = 70 × 10 (, years). .

Care must be taken, however, that anomalous gradients such as exist around faults, unconformities and rising domes- are first delineated.

Although the salinity gradients are consistent in marine sands surrounded by massive shales, the maximum depth at which the salinity continues to increase is a more complicated entity. Figs. 1 and 2 show that the salinity maximum may exist at widely separated depths. This is somewhat in accord with the top of overpressure, which varies independently of depth of burial (and most geological) factors occurring at the time of deposition).
Efforts to Improve the Profitability of the Huizhou Fields
Authors: Chou Clement K. , Liu Defu , Zhai LingShen , Duan Chenggang
Published: December 2007

The Huizhou 21 — 1 oil field is one of the first offshore oil fields to be developed in the South China Sea. After start—up of production from HZ/21 — 1 in 1990, four adjacent oil fields have been developed and tied into the original infrastructure. The Huizhou Fields were developed and are operated by a joint venture between China Offshore Oil Nanhai East Corporation (CONHE) and ACT Operators Group, which is jointly owned by three Western oil companies ( A gip, Chevron, Texaco).

Even though oil prices have been much lower than originally forecasted, ACT and CONHE have been able to mitigate the impact of lower oil prices on the financial performance of the Huizhou Fields. This is due to better — than — expected reservoir performance, continuous efforts to update and improve the development plan, and cost—effective integration of new fields into the existing infrastructure. This case study describes how the development plan has evolved and the continuous learning process that CONHE and ACT went through to optimize economic benefit.
Commercial Test of Polymer Flooding in Daqing Oil Field Daqing petroleum Administrative Bureau
Authors: Wang Demin , Zhang Jingcun , Meng Fanru , Liu Heng , Li Lin , Han Bohui , Qi Lianqing
Published: December 2007

Wang Demin, SPE Member, Zhang Jingcun, Meng Fanru, Liu Heng, Li Lin, Han Bohui, Qi Lianqing

Commercial pilot test of polymer flooding in Daqing oil field has been conducted for nearly two years, this paper summarizes the operating procedures and its initial results. Although this test is far from completion, it is successful according to the analysis of the obtained data which is marked by dramatic decrease of watercut of oil wells, increase of oil production by times, and accordance of the production behaviour with the predicted value on the whole. This test provides excellent prospects for large scale polymer flooding in Daqing oil field.

Introduction

Daqing oil field is a heterogeneous sandstone reservoir formed by "fluvial delta system", and is characterized by low reservoir temperature, low salinity of formation water and medium viscosity of crude oil, which are favourable geological characteristics for polymer flooding.

Four small scale polymer flooding pilot tests have been conducted in Daqing oil field from 1972 to 1993, and have obtained relatively good results, recovery rate was increased by more than 10%, and incremental oil for each ton of polymer was more than 150 tons.

For many years, polymer screening, polymer degradation and core flooding by polymer have been studied in the laboratory, which have provided theoretical basis for pilot tests.

To prove the polymer flooding result under condition of current well pattern and well spacing of the oil field, which is "large well spacing and many well groups", and to provide practical basis for commercial polymer flooding, preparation for this commercial test began to be made from 1990.

Polymer flooding was started in January 1993, and the test is presently under way.

RESERVOIR DESCRIPTION AND RESIDUAL OIL DISTRIBUTION

The test area is located in the northern part of Saertu oil field and the test layers are Pu l (Fig. 1). This areal was put into development by line well pattern water injection in 1963. From the end of 1990 to the beginning of 1991, 50 new wells were drilled to conduct this commercial test, consisting 25 five-spot area well patterns with an injection production well spacing of about 250 m. There are 61 production and injection wells together in the test area, among them 25 are injection wells (including one original injection well and three converted injection wells), 36 are production wells (including eight original production wells).

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Alkaline-Surfactant-Polymer Combination Flooding For Improving Recovery of the Oil with High Acid Value
Authors: Wanchao Song , Chengzhi Yang , Dakuang Han , Zhijian Qu , Baoyu Wang , Wenluo Jia
Published: December 2007

Study in this paper, alkaline-surfactant-polymer combination system (ASP) as a flooding agent, is a new EOR technology aimed at oil with high acid value. Study has been proved that flooding system's rheology and IFT between flooding system and oil with high acid value are key factors effecting oil recovery. Formation of petroleum carboxylic soap from reaction of alkaline with organic acid in oil, petroleum sulfonate sodium and tritron system (OP-10) added in and their combination effect result ultra-low IFT even at very low surfactant concentration (transient IFT less than 10−4mN/m, balanced EFT as low as 10−3−10−2mN/m). Appropriate concentration of partly hydrolyzed Polyacrylamide (PAM) could significantly increase viscosity of flooding agent. Combination effect of both greatly increased capillary number which restricts residual saturation. Presence of alkaline obviously decreased surfactant loss in porous media. Oil recovery of physic simulation augmented by over 16% (OOIP). Net oil augmentation of 20667.7t has been obtained from a pilot area in an almost abandoned water flooding field of Gudong, Shandong Province. Oil recovery from central area increased by 13.4%.
Batch Drilling and Positioning of Subsea Wells in the South China Sea
Authors: Hughes John D. , Coleman Rod A. , Herrmann Robert P. , Macfarlane Andrew M.
Published: December 2007

This paper describes the initial phase of a multi-well subsea development using a building block technique. This phase included the setting of the conductors for all 20 wells, manifold piles and pipeline bases and the drilling of 15 wells to various stages of completion. Offshore operations were conducted in batches to maximize efficiencies and economies of scale. The emphasis of this paper is on the jetting operation of the conductors and the positioning techniques used to meet the requirements of the later phases of the building block process.
Development of Ultra-low Permeable Reservoir in Ansai Oil Field
Authors: Mingzhi Tao , Zhengyun Song , Zhiyu Wu
Published: December 2007

Generally, the reservoirs with permeability lower than 50× 10-3µm2 is called low permeable oil field. Ansai oil field in which the average permeabihty is about 1.29× 10-3µm2 is classified as ultra-low permeable oil field. Despite many low permeable reservoirs were discovered in early days, they haven’t been effectively produced due to the complicated production technology and low profit. However, with the development of petroleum industry, the technologies of developing low permeable reservoirs have been improved, particularly, the progress of fracturing and water injection, the production of low permeable reservoirs has been rapidly developed. This paper aims to overview the reservoir, fracturing and water injection, describe the key methods used in production of Ansai ultra-low permeable reservoirs, including the results of water injection.
Development of Jidong Oilfields with Complicated Fault-blocks
Authors: Shoude Yu , Bin Li , Qilong Zhang , Ruoxia Wu
Published: December 2007

Jidong is a rather complicated fault-block oil producing area which is characterized by broken structures, multiple reservoir types, complicated oil-water systems, big lateral changes, deeply buried major oil layers, severe heterogeneity and varied fluid properties. In addition, more than 80% of the wells are directional due to the limit of surface conditions, which gives more difficulties to the development of Jidong area.

Therefore Comprehensive study of multi-disciplines has been used in Jidong to improve early reservoir evaluation and development. Application of advanced technologies and theories such as production seismic, loggings, production tests, limit test, structural sedimentology, fine reservoir description, numerical simulation and contagious wells distribution has enhanced study of enrichment pattern of oil and gas. The strategy of progressive exploration and development has been adopted through "Integral planning, partial implementing, well-aimed studying, timely adjusting and gradual improving". Since 1989, the success rates of development wells has been over 95%.
A Production Allocation Method for Commingled Gas Completions
Authors: Prabowo H. S. , Rinadi M.
Published: December 2007

This paper presents a method to approximate the ratio of flow rate and cumulative production for each reservoir in a commingled gas completion. Numerical reservoir simulation was used to describe flow rate and pressure response of wells completed in multiple producing reservoirs without inter-layer crossflow. The use of the method is illustrated to compare the results of simulated and field data.
Yacheng 13-1 Gas Project
Authors: Bass J. W. , Peisheng Zhang
Published: December 2007

In 1982 the Peoples' Republic of China awarded ARCO China Inc. the first-ever concession for offshore oil exploration by a foreign company. This historic event led to discovery of the 3 TCF Yacheng 13-1 gas field by ARCO China Inc. in 1983. This paper describes the US$1,125 billion Yacheng 13-1 Gas Project that will start-up in late 1995, some 1214 years after field discovery.
Modifying Set Cement Performance for Improving Cementing Job Quality
Authors: Shi Guodong , Liu Wenjun , Gao Yonghui
Published: December 2007

Hydration process of cement takes place once it is mixed with water, forming set cement gradually. The hydration process will last for quite a long time after setting. During the hydration process, cement hydrate, internal pore structure, apparent volume, and its mechanical performance still keep changing. The performance of set cement is also affected by the changing conditions caused by the subsequent projects or development operations, so it is important to research into the long-term performance of set cement and take some measures to improve cementing job quality.
Integrating Geoscience and Engineering for Improved Field Management and Appraisal
Authors: Gawith D. E. , Gutteridge P. A. , Tang Z.
Published: December 2007

Efficient field management and appraisal rely on a good understanding of reservoir geology and recovery efficiency. This requires co-operation and good communication between different disciplines. This paper presents and demonstrates the shared earth model approach, to encourage integration and co-operation between disciplines producing more reliable reservoir characterisation and performance prediction. A North Sea field is used as an example to illustrate the development and use of the shared earth model. The way in which it brings together the subsurface disciplines is shown by dynamic data feedback and seismic validation of simulator predictions.
Analytical and Numerical Solutions for Estimating the Gas In-Place for Abnormal Pressure Reservoirs
Authors: Elsharkawy Adel M.
Published: December 2007

Gas reservoirs with abnormally high-pressure have been encountered all over the world. For these reservoirs, a straight line plot of P/Z Vs. Gp for the early production data and extrapolation to zero reservoir pressure project incorrect, IGIP, initial gas in place. The P/Z plot is based on the assumption that gas compressibility is the "Sole" reservoir drive mechanism. In abnormal pressure gas reservoirs, however, grain expansion, formation water expansion, and water influx from shale or small associated aquifer, in addition to gas expansion contribute significantly to the gas production. Several material balance models have been proposed to calculate the initial gas in place for abnormally high-pressure gas reservoir. The present study is concerned with analyzing the different material balance models used to estimate the IGIP for these kind of reservoirs. Therefore, it reviews the bases and assumptions on which these models have been developed, as well as discusses the strength and weakness of every model. In addition, the present study comprises calculations of the IGIP by analytical and numerical models of the material balance equations for eight case histories. The study shows that solution plot of Havlena and Odeh can be used to estimate the IGIP for abnormal pressure gas reservoirs without prior knowledge of the aquifer size or the formation compressibility. Moreover, the present investigation reveals that most of the material balance models analyzed in this study are sensitive to the value of the initial reservoir pressure and the early data. Unfortunately, this is the time when reliable estimate for the IGIP is vital for economic decision regarding the development of such gas reservoirs.
Technical and Economic Aspects of the Flexible Export Pipeline System for Amoco's Liuhua 11-1 Development Offshore China
Authors: Bludworth Charles , Lecomte Hubert , Kolanski Henry
Published: December 2007

The flexible pipe approach can provide many technical advantages and cost savings over a rigid pipe approach when considered early for a project.

One such project is the Liuhua 11-1 Oil Field, located offshore China in 1000-foot water depth, which is being developed jointly by Amoco Orient Petroleum Company (AOPC), China National Offshore Oil Corporation (CNOOC), and Kerr McGee.

This paper presents a comparison of technical and cost issues examined by the project team during the bid stage of the project.

In addition, this paper details the technical challenges, and their solutions for the engineering, manufacturing and installation of Coflexip's flexible export pipe lines and flexible risers.
Exploration of A Seaice Hazard Warning Program For Winter Production in The Bohai Oil Fields
Authors: Tongkui Li
Published: December 2007

The existing offshore oil/gas fields in production in the Bohai Sea are all confronted with sea ice problems in the cold years. The development of a sea ice state warning system for the winter oil production in these fields is discussed in the paper on the subsidiary topics as: the skeleton of the system, monitoring and forecasting of the sea ice condition and the offshore structural behaviours, the criteria of warnings, and the database and software networks. The system is developed for various types of offshore structures and different oceano—geographical regions in the Bohai Sea.
Well Performance Analysis and Deliverability Monitoring for Layered Reservoirs Without Crossflow
Authors: Thrasher T. S. , Tompkins M. W. , Wang G. S.
Published: December 2007

This paper presents a case history study that demonstrates monitoring bottom-hole well deliverability performance for flowing oil-wells completed in layered reservoirs. The field of study is the recently developed Xijiang 24-3 Field, offshore China in the Pearl River Mouth Basin. Development of the bottom-hole backpressure curve for individual layer packages and total well are presented as a reservoir management tool. A combination of individual layer production well tests, production logging tool (PLT) measurements and permanent downhole bottom-hole pressure readings are utilized to develop the total well bottom-hole backpressure curve. Pre-gravel pack and post-gravel pack results are discussed and compared to daily production measurements. The bottom-hole backpressure curve is shown to be an effective reservoir management tool to monitor well and reservoir performance.
Technologies Used in the Production of High Pour Point Crude Oil in Shenyang Oilfield
Authors: Hongen Dou
Published: December 2007

Shenyang oilfield characterigzeed by the high pour point up to 67 °C as one of the oilfields seldom seen in the world, it was developed in the end of 1980s’. The paper reviews the production technologies developed and applied successfully in Shenyang oilfield during its ten-year production hostory, including artificial lift, Stimulation production, well testing and systematic adjustment. A prospect of this oilfield's future production is also presented in this paper.
Reservoir Engineering Aspects of Horizontal Wells – Application to Oil Reservoirs with Gas or Water Coning Problems
Authors: Peng C. P. , Yeh N.
Published: December 2007

Horizontal drilling had a high profile from the late 1980s onwards in the tight, fractured reservoirs of the Austin Chalk and the Bakken Shale. Today this technology is being increasingly applied in thin or highly permeable oil reservoirs where there is a need to minimize drawdown to prevent water and gas coning, while at the same time maximizing well productivity.

Horizontal wells have been drilled in relatively thin, high permeability reservoirs such as Helder and Troll in the Dutch and Norwegian sectors of the North Sea respectively. They have been used to improve oil productivity and drainage from the low permeability conglomerates in the North Brae field in the U.K. sector of the North Sea. In Canada, they are being used in the recovery of both light and heavy oil reservoirs, while in Alaska they are being used at Prudhoe Bay to reduce gas coning while maximizing production rates. The world over, from Europe to Argentina to China to Australia, new applications have been found for this production technology barely out of its infancy.

This paper reviews both the theoretical and practical planning considerations necessary for a successful application of horizontal wells. The use of horizontal wells in reservoirs with gas or water coning problems is emphasized.
Using Close Spacing Well Logging Curves To Finely Develop Fluvial Fades Reservoir Sedimentation Models
Authors: Hanqing Zhao , Zhiguo Fu , Guangyun Wang
Published: December 2007

A great majority of the productive reservoirs in Daqing Oilfield are composed of various kinds of fluvial channel sandstones. Under the condition of no outcrop, lack of analogous modern deposits available for detailed investigation, basing on the rich experiences of our research on reservoir sedimentary facies, as well modern fluvial sedimentological knowledge, a new research method is developed, that is, taking advantages of logging curves of close well pattern on a large area, and to gradually analyze sandbody geometries and their internal architectures, and to finely construct sedimentation models of fluvial facies reservoirs, and to describe reservoir heterogeneity finally. By applying this to subsurface reservoirs in large scale, four types of sedimentation models of fluvial channel sandbodies in PI1–3 zones are systemically constructed. Infill drilling and production test data have proved the credible accuracy and wide adaptability of the models.
Data processing, Diagnosis and Optimum Design of Rod String for Numerically Controlled Pumping Wells
Authors: Yugeng Li , Xiaoqing Yu , Wanggeng Wan , Yuangang Xu , Guoan Yu
Published: December 2007

The structure, characteristic and primary parameters' determination are briefly introduced for Numerically Controlled Pumping Unit is this paper. After data processing of diagnostic results for Numerically Controlled Pumping Unit, a diagnosis software and a software for designing the tapered rod string are developed. It is proved that these two softwares are reliable and have enough precision.
ESP Run Life Maximisation for the Xijiang Field Development
Authors: Heuman W. R. , Moore E. R. B. , Yue Y. , Hirshblond S. P.
Published: December 2007

Traditionally the operator and the supplier of ESP systems have not necessarily had the same goals and objectives with respect to maximising ESP run life. A longer run life means reduced costs and downtime for the operator while a shorter run life provides the ESP supplier with the opportunity for equipment sales.

This paper will describe the Quality Assurance Programme which has been implemented in the Xijiang Project to ensure ESP run life maximisation. The Performance Based Contract that is being utilised between the operator and the ESP supplier will be addressed, as it is a key factor in providing the economic incentive necessary for the ESP supplier to strive to maximise ESP run life. Other key factors responsible for reducing the learning curve associated with ESP operations will be discussed. A summary of the results achieved and the conclusions reached from the implementation of the ESP Quality Assurance Programme will also be covered.
The Progress And Prospect Of Equipment Manufacturing In China For Oil And Gas Exploration And Production
Authors: Zhiqian Huang
Published: December 2007

Petroleum equipment plays a critical role in the oil and gas exploration and production activities. Through more than 40 years' efforts, a manufacturing system including more than 50 manufacturing plants have been established by China National Petroleum Corporation (CNPC), producing around 70% different equipment and instrumentation required for oil and gas exploration and development in China. In this paper, the progress of developing and manufacturing those equipment has been reported, including the developing strategy, the present status of exploration, drilling, production and oilfield surface engineering equipment manufacturing. The prospect in this area has been reported as well.
Low Invasion, Synthetic Oil-Base Mud Coring in the Yacheng 13-1 Gas Reservoir for Gas-in-Place Calculation
Authors: Rathmell J. J. , Bloys J. B. , Bulling T. P. , Parr J. J. , Pasternack E. S. , Jerauld G. R. , Sakurai S.
Published: December 2007

The low invasion coring method was used to provide highly reliable connate water saturation in the Oligocene age, Lingshui III sandstone, Yacheng 13-1 reservoir, development Wells A1 and A2. Development well coring was implemented to resolve an uncertainty in the total gas-in-place.

A synthetic oilbase mud was designed to simultaneously operate at the 350°F wellbore temperature, provide reliable core connate water saturation, insure high quality well logs and minimize formation damage. The polyalphaolefin (PAO) synthetic base oil is biodegradable and is less damaging to the environment than diesel or mineral oil.

Procedures for obtaining a low invasion core in a remote location are described. Careful planning and execution are necessary for successfully obtaining low invasion core.

This is the first use of low invasion oilbase mud coring in China. Water saturations from cores are essential to accurately calculate the gas reserves. Possible gas-water contact variations cause uncertainty in connate water saturation from capillary pressure. Salinity variations in the reservoir complicate the calculation of connate water saturation from electrical logs. Accurate water saturation and salinity data from cores are needed to develop log models that can be applied in non-cored wells.
Analysed and Fractal Singlle Point Method for Solving Hydraulic Problems in Ocean Engineering
Authors: Yuhua Fu
Published: December 2007

This paper presents two kinds of Single Point Method (SPM), i. e. analysed SPM and fractal SPM, and decides the analysed solution and fractal distribution on any solitary point for problems in ocean engineering. The analysed SPM is according to the optimization method of weighted residuals for solitary point, and gives the hydraulic equation's solution for any solitary point (point solution) which is suitable only for that solitary point. As the solution for solitary point is being development independently, it does not need to consider the compatibility with other points, but total boundary conditions and the supplementary derived residual equations and derived boundary equation which were got by running the derivative operations to the differential equation and boundary conditions should be taken into account. The fractal SPM is according to multifactor variable dimension fractals, and decides the fractal distribution of some physical quantities on any solitary point for hydraulic problem. It is differentiated from the existing fractal method (contains one factor and the fractal dimension is a constant) by that the different factors (characteristic scales) correspond with different fractal distribution and for different fractal distributions the fractal dimension Di are the function of characteristic scale Ri.
Enhanced Hydraulic Fracture Technology for a Coal Seam Reservoir in Central China
Authors: Wright C. A. , Tanigawa J. J. , Shixin Mei , Zhigang Li
Published: December 2007

Economic gas production from coal seams (in which cavitation is not applicable) requires hydraulic fracture stimulation due to the low reservoir permeability of most target coal seams. Effective hydraulic fracture stimulation of coal seams, however, presents a formidable challenge due to a number of factors including: the mechanical complexity of coal; prevalent natural fracturing; extreme sensitivity of coal seams to fracturing fluid damage; stress sensitive permeability of coal; and the (often) complex geometry of the induced hydraulic fractures.1

The authors began by performing an in-depth analysis of previous hydraulic fracturing treatments performed in coal seam reservoirs in China. The results of this post-treatment analysis, together with the collected reservoir data, led to the development of a modified stimulation strategy. As part of a pilot investigation by the North China Bureau of Petroleum Geology (NCBPG) of a (potentially) large coalbed methane field in China, eight hydraulic fracturing treatments were executed in the summer of 1994 using the modified stimulation strategy -- including on-site real-data three-dimensional hydraulic fracture modeling and treatment re-design.

This paper describes the analysis theory and methodology, the novel stimulation techniques employed, the on-site implementation (including difficulties), and the results of the fracturing treatments. While the paper is a case study of fracturing at a particular field, the paper will also contain a discussion of some of the complexities of coal seam fracturing. The issues to be discussed are: simultaneous propagation of multiple hydraulic fractures; (often) excessive near-wellbore fracture tortuosity; rapid downward proppant convection; and the high net fracturing pressures which may result in exceeding more than one of the reservoir's principle stresses.

Analysis of the collected data shows that 2-D models and "conventional" 3-D models of the hydraulic fracturing process apply very poorly to hydraulic fracturing in coal seams. Engineering decisions based on these more "conventional" fracture modeling techniques can lead to inappropriate fracture treatment design, as well as significant problems in predicting the post-frac production performance. The paper summarizes a few enhancements to coal seam fracturing technology, as well as the present limitations and the necessary advancements required for superior coal seam fracture performance in the future.
Plate Tectonics Affect on Drilling and Production Operations
Authors: Barnett Richard D. , Adil Imtiaz
Published: December 2007

From the time that Union Texas Pakistan Inc., began operations in Badin, UTP personnel have observed several anomalies which are inconsistent with experience gained from drilling and production operations in other areas, i. e. the experience gained while working in relaxed sedimentary basins.

There are several recognizable differences between Badin and relaxed sedimentary basins, and these vary from subtle to gross. These include: High fracture gradients.Bore hole breakout and its ability to often predict the location of porosity/permeability.Bore hole elongation.Shape of drill cuttings.

The apparent reason for these differences is the high horizontal stresses. These high horizontal stresses effect many drilling and production operations.

This paper will discuss the techniques used to identify these various stresses and some of the affects they may have on drilling and production operations.
High Energy Gas Fracturing(HEGF): Mechanism and Practice
Authors: Li Dang , Zhao Gang , Yang Weiyu
Published: December 2007

HGEF, an oil/gas well stimulation technology by means of powder and/or propellant in well to create multiple radial fracture system in the vicinity of weelbore and hence to increase the well production, has been widely tested both home and abroad and shown a bright prospect in oil and gas industry. This paper deals with some foundamental aspects of HEGF, including technology base, key factor of HEGF, influence of HEGF on casing and cement, flow regime of the multiple radial fracture system and the relationship between charging and pressurization. Based on the results of our researches and field applications, we hope that more attention should be paid to this stimulation technology.
Engineering Applications for Integrated Reservoir Characterization
Authors: Ehlig-Economides Christine A.
Published: December 2007

With data acquisition at many scales, comprehensive databases, and integrated data visualizations, a much more realistic understanding of the implications of reservoir characterization on production is emerging. This paper provides a multidisciplinary overview of four tasks: reservoir delineation, reservoir modeling, production optimization, and uncertainty analysis. Each of these tasks highlights specific engineering applications. An overview is provided of geophysical, geological, and petrophysical approaches that engineers need to understand in order to communicate effectively with geoscientists. Flow units and compartments are the key elements used in this paper to relate the reservoir characterization provided by geoscientists to what is needed by engineers. These two concepts enable engineers and geoscientists to develop a common view of what various disciplines can reveal about a reservoir.

Applications for integrated reservoir characterization include improving drilling and completion locations, optimizing well productivity, and enhancing recoverable reserves. An integrated reservoir characterization focused on flow units and reservoir compartments amplifies considerably what can be understood from conventional engineering techniques, including reserves estimation, material balance, production data analysis, and fluid flow simulation.

Examples from field studies demonstrate results derived from integrated reservoir characterization that would not have been apparent from conventional engineering methods.
Quantitative Description for the Heterogeneity of Pore Structure by Using Mercury Capillary Pressure Curves
Authors: Pingping Shen , Kevin Li , Fenshu Jia
Published: December 2007

Pore structure of reservoir rock is one of the most important factors to affect microscopic oil and water flowing in porous media and the development efficiency of an oil field developed by water injection. There are now many methods for describing pore structure. However, much attention is being paid to develop better and more efficient methods. Fractal dimension has been used to quantitatively describe the heterogeneity of pore structure in this paper. It has been showed that the larger the fractal dimension of pore structure, the more heterogeneous the pore structure for sandstones, sandstones with gravel and pinhole dolomite rocks. The fractal dimension of pore structure is calculated from the mercury-injection capillary pressure curve of the rock.

The typical two-section fractal behaviour of sandstone pore structure in Lamadian Oilfield, Daqing has been studied in this paper. It has been found that there is a good correlation between the fractal dimension of large pores with fractal behaviour and the oil recovery at water breakthrough while there is also a good relationship between the fractal dimension of the small pores with fractal behaviour and irreducible water saturation. This shows that the large fractal pores affect the amount of oil recovery at water breakthrough and the small fractal pores affect the amount of irreducible water saturation for this type of sandstones from Lamadian Oilfield. It has also been found that there is no relationship between the fractal dimension of pore structure and the oil recovery at water breakthrough if the pore structure of sandstone from Lamadian Oilfield was treated as one-section fractal structure.
Polytropic Flow Of Natural Gas In Vertical Pipes
Authors: Adair John K. , Power Harry H.
Published: December 2007

A method is presented for calculating the flowing bottom hole pressure in natural gas wells using a polytropic equation of state. The polytropic equation is based on an empirical exponent and is determined by using the point functions of pressure P, temperature T and compressibility factor Z at the terminals of the vertical flow string.

A comparison of calculated and field measured results were made on gas well data presented in the literature. The average percent deviation between the calculated and observed flowing bottom hole pressures was 0.416.

The polytropic method may use any compressibility factor correlation applicable to the fluid under study, which is important when the amount of inerts is appreciable.

An example demonstrating the polytropic method is presented-using friction factor correlations which are based on an absolute pipe roughness of 0.0006 in.
New Analysis Method for the Vertical Fracture Well
Authors: Yue-wu Liu , Ci-qun Liu
Published: December 2007

The pressure transient behavior of hydraulically fractured wells has been the subject of considerable study over the recent years. Several investigators have presented solutions of the fundamental equations, identified qualitative diagnostic trends and suggested integral techniques. This paper presents a new method to solve the problem of analysis of well test data of the hydraulically fractured well.

The new mathematical model for the vertically fractured well in the dual-porosity and homogeneous reservoirs was founded by using the elliptic flow model and the integral method of conservation mass. The solution for the new model was obtained in real space. The type curves for the vertically fractured well in both homogeneous and dual-porosity reservoirs with and without wellbore storage and skin effect were calculated. In order to consider the wellbore storage and skin effect, the techniques of Laplace numerical transformation and Laplace numeral inversion were used. The special results for homogeneous reservoir have been identified by compared with the results of other authors, such as the infinite conductivity solution of A.C. Gringarten, the finite conductivity solution of H. Cinco-ley and the finite conductivity solution of M.J.Economades which considered the wellbore storage. They all have the same identities. Two field examples are used to illustrate the use of the new method.

The characteristics of the type curves for both homogeneous and dual-porosity reservoir are described. For the dual-porosity reservoir, the type curve presents seven flow periods: the wellbore storage controlled period, the skin effect controlled period, the bilinear flow period, the first transient period, the dual-porosity characteristic flow period, the second transient flow period, and the radial or pseudo-radial flow period.

The solutions have the following advantages: The solution may be used for both homogenous and dual-porosity reservoirs, and for both infinite and finite conductivity vertical fracture. The range of the dimensionless conductivity is from 0.001 to 500. Even more, the type curve is quickly calculated by using this method than any others. The new sets of type curves can be directly used in the oil field.
Water-Oil Capillary Pressure and Wettability Measurements Using Micropore Membrane Technique
Authors: Longeron Daniel , Hammervold Wibeke L. , Skjaeveland Svein M.
Published: December 2007

This paper describes a new technique to simultaneously measure the capillary pressure curves and wettability indices for an oil – brine – rock system. By improving the porous plate method, the full cycle of four capillary pressure curves, i.e. spontaneous and forced drainage and imbibition, is measured in days instead of months. This is achieved by the use of thin oil- and water-wet micropore membranes and short samples with large diameter.

Measurements have been done on sandstone and carbonate cores with wettabilities ranging from strongly water-wet to oil-wet. A reduction in experimental time by a factor of 10 or more is gained by the new method for a full cycle of the four capillary pressure curves.

In addition, a new measure of wettability is suggested as an improvement of the USBM test, incorporating all four areas between the capillary pressure curves and the saturation axis. The new wettability index may be conceived as an extension of the Amott test, with the four saturation intervals weighted by the corresponding areas under the capillary pressure curve and may better discriminate between mixed-wet and spotted-wet samples.
Prediction on the Reasonable Flow Rate and Productivity of Single Well in the Gasfield of Central Shan-Gan-Ning Basin
Authors: Keqiang Yu
Published: December 2007

According to the productivity equation established by the modified isochronal test (MIT) in the Gasfield of Central Skan-Gan-Ning Basin, the gas well type curve can be generated and the reasonable flow rate of a gas well can be known from the curve. The correlation between reasonable flow rate and absolute open flow potential (qAOF) is also established. The statistic analyses of the correlation between qAOF and kh from the well test and between qAOF and the coefficient b in the binomial productivity equation have been done with this study and the correlations between them have therefore been set up. By using the correlations, the productivity of the new well can be forecasted.
Experimental Measurement of Coal Matrix Shrinkage Due to Gas Desorption and Implications for Cleat Permeability Increases
Authors: Seidle John P. , Huitt L. G.
Published: December 2007

Coal is not an inert reservoir rock and reacts to gas des-orbed from its surface. Coal matrix shrinks as gas is desorbed, increasing cleat width and, therefore, permeability. Very few coal matrix shrinkage data have been reported in the literature so a series of experiments was undertaken to measure such data at reservoir pressures, temperatures, and 100% relative humidity. Strain gages were affixed to the coal sample in the face and butt cleat directions as well as the vertical direction. This work reports measured deformations of a sample of high volatile C bituminous coal from the San Jan Basin during sorption and desorption of first methane then CO2. A pressure cycle was also run with helium, a nonsorbing gas, to determine mechanical compliance of the sample. Observed strain gage behaviors are discussed and shrinkage coefficients for both gases reported. Matrix shrinkage was found to correlate with gas content rather than pressure, confirming the work of a previous investigator. Shrinkage coefficients varied more among replicate gages aligned in the same direction than between gages in different directions. Anisotropic shrinkage effects are discussed. Using a matchstick geometry model, equations are derived for permeability change due to matrix shrinkage. Coefficients reported here are used in example calculations of absolute permeability and porosity increases during coalbed depletion.
Net Present Value Probability Distributions From Decline Curve Reserves Estimates
Authors: Simpson D.E. , Huffman C.H. , Thompson R.S.
Published: December 2007

D. E. Simpson, C. H. Huffman, and R. S. Thompson

SPE Members

This paper demonstrates how reserves probability distributions can be used to develop net present value (NPV) distributions. NPV probability distributions were developed from the rate and reserves distributions presented in SPE 28333. This real data study used practicing engineer's evaluations of production histories. Two approaches were examined to quantify portfolio risk. The first approach, the NPV Relative Risk Plot, compares the mean NPV with the NPV relative risk ratio for the portfolio. The relative risk ratio is the NPV standard deviation () divided the mean () NPV. The second approach, a Risk - Return Plot, is a plot of the discounted cash flow rate of return (DCFROR) versus the a for the DCFROR distribution. This plot provides a risk - return relationship for comparing various portfolios. These methods may help evaluate property acquisition and divestiture alternatives and assess the relative risk of a suite of wells or fields for bank loans.

Introduction

Reserves acquisition and divestiture decisions are based on many factors including corporate strategy, risk, the company's financial position and cash flow requirements. The value of a prospective acquisition or divestiture is uncertain since it depends on factors such as future oil prices, production rates, and discount rate that must be estimated. To quantify risk, NPV probability distributions were developed from the rate and reserves distributions presented in SPE 28333, "Probability Ranges for Reserves Estimates From Decline Curve Analysis."

Two approaches were examined to quantify portfolio risk. The first approach, the NPV Relative Risk Plot, compares the mean () NPV with the NPV relative risk ratio for the portfolio. The relative risk ratio is the NPV standard deviation (a) divided the NPV. The second approach, a Risk - Return Plot, is a plot of the discounted cash flow rate of return (DCFROR) versus the a for the DCFROR distribution. This plot provides a risk - return relationship for comparing various portfolios.

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