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    20 February 1999, Volume 21 Issue 1
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    油气藏工程
    ENGINEERING GEOLOGICAL CHARACTERISTICS OF TIGHT GAS SANDSTONE RESERVOIRS IN WESTERN SICHUAN BASIN AND STRATEGY OF FORMATION DAM-AGE CONTROL
    Kang Yili Luo Pingya Yang Yong Wang Ping
    1999, 21(1):  1-5.  DOI: 10.3863/j.issn.1000-2634.1999.01.001
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    Formation damage has been recognizes as one of the key factors limiting the efficiency of exploration and development for natural gas in tight sandstones. A comprehensive research on the engineering geological conditions of tight gas sandstone reservoirs in western Sichuan Basin revealed the following characteristics:①existence of multiple pay zones differing markedly in thickness and areal extent;②abnormally high formation pressure and multi-pressure systems;③capillary pressure increasing sharply with increased burial and decreased permeability of the reservoirs;④fractures occurring heterogeneously,with microfractures being the major contributor of reservoir permeability;⑤strong water and alkaline sensitivity related to abundant clays, and⑥reservoir permeability being very sensitive to variations in stress conditions. Analyses indicate that horizontal wells, gas based working fluids, and temporary shielding techniques are suitable for the protection of such tight gas sandstone reservoirs.

    FORMATION OF UNDERPRESSURED FLUID COMPARTMENTS AND ITS RELATION WITH SHALLOW OIL AND GAS ACCUMULATIONS: HONGNAN-HONGXI AREA,TURPAN-HAMI BASIN AREA
    Li Yanjun Chen Yicai Huang Jianquan Yang Yuancong
    1999, 21(1):  6-9.  DOI: 10.3863/j.issn.1000-2634.1999.01.002
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    A comprehensive analysis of the underpressured fluid compartments in Hongnan-Hongxi area of the Turpan-Hami Basin indicated that, within this area which had not experienced prominent denudation, the genesis of underpressured compartments were mainly related to hydrocarbon diffusion. In addition, over-compaction and small-range tectonic uplifting had intensified the underpressure. It is shown by this work that petroleum migration and pool formation has a close relationship with these underpressured compartments.

    ESTABLISHING A GENERAL MODEL OF PERMEABILITY FOR SAND-SHALE FORMATIONS
    Liu Xiangjun Xia Hongquan Zhao Zhengwen
    1999, 21(1):  10-12(2.  DOI: 10.3863/j.issn.1000-2634.1999.01.003
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    On the basis of analyzing the available formula of permeability, the feasibility and method of establishing a general model of permeability prediction have been investigated by using mathematical tools. The results show that the proposed model,which employs the 2-D trend surface analysis, not only deals
    with the problem better, but also yields higher precision in permeability prediction.

    DEFINITION OF DISINTEGRATED ROCK MASS AND THERMODYNAMIC ANALYSIS OF ROCK DISINTEGRATION
    Wang Pingquan
    1999, 21(1):  13-16.  DOI: 10.3863/j.issn.1000-2634.1999.01.004
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    The concept of disintegration and disintegrated rock mass is put forward in accordance with the practice of geotechnical engineering, geotechnical mechanics, rock mechanics and civil engineering. The failure modes and lost-stabilization types for disintegrated rock mass are discussed. According to thermodynamic principles and from the viewpoint of microscopic struc-
    ture, the process of rock disintegration is virtually a kind of internal energy dissipation, and the realization of disintegration means that a partial energy is dissipated to produce new cracks.The steady criterion for disintegrated rock mass is proposed.

    NUMERICAL SIMULATION STUDY OF WATER INJECTION DEVELOPMENT IN AN EXTREME-LOW-PERMEABILITY FRACTURED RESERVOIR, XIAOGUAI OILFIELD
    Zhang Hongmei Jiang Xiaohui Yang Yu
    1999, 21(1):  17-20.  DOI: 10.3863/j.issn.1000-2634.1999.01.005
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    The Xiazijie Formation oil pool in Xiaoguai oilfield is a low-porosity, extreme-low permeability, fractured conglomerate reservoir. Based on detailed geological reservoir description and production performance data, the authors investigate the factors influencing the production of the oil pool with CMG’s black oil model (IMEX) . Variation and sensitivity of such factors as IPR, location of water injection, production rate, well pattern,direction of well array in relation to fracture orientation and recovery method ( solution gas drive vs. water injection) are analyzed.
    INFLUENCE OF INJECTION RATE ON WATERFLOODING DEVELOPMENT OF LOW PERMEABILITY OILFIELDS
    Deng Ying-Er Liu Ciqun
    1999, 21(1):  21-24.  DOI: 10.3863/j.issn.1000-2634.1999.01.006
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    The existing theory of waterflooding is based on Darcy’slaw. However, studies and oilfield development practice have shown that in low permeability reservoirs the flow does not follow Darcy’s law, with a starting pressure gradient (SPG) occurring in the process. With SPG taken into account, this work formulates the method of calculating indices of waterflood devel-
    opment before and after water occurs in the well array, under the condition of constant injection rate. Application of the formulas is illustrated with an example. Influence of injection rate on waterflood recovery is discussed. The results show that SPG has marked influence on the indices; and that there is an optimum injection rate at which the indices are most effective.

    NUMERICAL SOLUTION FOR A MATHEMATICAL MODEL OF FLOW IN LOW PERMEABILITY GAS RESERVOIRS
    Li Tiejun Wu Xiaoqing
    1999, 21(1):  25-28.  DOI: 10.3863/j.issn.1000-2634.1999.01.007
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    A mathematical model of fluid flow in low permeability gasreservoirs is developed, with gas slippage effect taken into consideration. A numerical solution for the model is provided.Analysis and computation show that the algorithm used has a high level of accuracy and consistency, and thus can serve as a theoretically reliable tool for the study of gas flow in low perme-
    ability reservoirs.

    LOOKING FOR RESIDUAL OILS WITH NON-BOUNDLESS TRIELECTRODE SECTION METHOD USING THE DRILLING CASING AS ELECTRODES
    Zhang Tianlun Zhang Bailing Nie li
    1999, 21(1):  29-34.  DOI: 10.3863/j.issn.1000-2634.1999.01.008
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    On the basis of a great number of aquarium analogue experiments, a novel D. C. electric resistance expecting method?the non-boundless trielectrode section method, which uses casing tubes in the wells as electrodes, has been developed by the authors. This paper reports and discusses the experimental results. It is indicated that for oilfields with regular well patterns this method may provide a cheap and efficient tool for thesearching of residual oils.

    地质勘探
    GENERATION AND EVOLUTION OF CARBONIFEROUS PETROLEUM SYSTEM IN EASTERN SICHUAN BASIN
    Li Yingying Lin Weicheng
    1999, 21(1):  35-38(5.  DOI: 10.3863/j.issn.1000-2634.1999.01.009
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    The Carboniferous petroleum system, with its formation and evolution largely controlled by the regional structural evolution, is one of the confirmed petroleum systems in eastern Sichuan Basin. The pool-forming history of this petroleum system can be divided into two stages. The first stage is from
    the Indosinian orogeny at the end of middle Triassic to pre-Himalayan movement, during which constant hydrocarbon accumulation towards the Kaijiang paleohigh occurred against a background of continuous growth of the paleohigh, resulting in the formation of areally extensive stratigraphic-structural combination pools within the Carboniferous strata. The second stage started in early Himalayan at the end of Oligocene, during which post-accumulation re-distribution of hydrocarbons took place to have formed the stratigraphic-structural combination pools and anticlinal pools on the Kaijiang paleohigh.
    NEW ANALYSIS ON THE COMPOSITION OF BEAN ROCK
    Chen Zhong Shen Mingdao Zhao Jingsong Tang Hongming
    1999, 21(1):  39-42.  DOI: 10.3863/j.issn.1000-2634.1999.01.010
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    A layer of so-called Mung Bean Rock was recently discovered at Hexidong in Daijiagou, Chongqing. The formation is about 1.5 m thick, in which many hard grains with diameter ranging from 2-5 mm can be easily seen. Compositional analyses show that the rock consists of illitic claystone, with an illite
    content of 95 -97%. X-ray refraction and SEM examination reveal that the main constituents of the grains are quartz (80%) and calcite (20%). This discovery provides not only a new site to investigate Mung Bean Rock, but also a potential industrial resource of illite.

    钻采工艺与设备
    RESEARCH ON THE SUPRA-HIGH PRESSURE CEMENTING TECHNIQUES
    Guo Xiaoyang Yang Yuanguan Yang Wansheng Zhang Hongsheng
    1999, 21(1):  43-47.  DOI: 10.3863/j.issn.1000-2634.1999.01.011
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    Within the North Tian Shan piedmont structural belt along the southern fringe of the Junggar basin, plastic claystone formations below the high geo-stress area have posed many difficulties on drilling and cementing operation. In order to achieve successful completion under such complex geologic conditions,the authors put forward six criteria in regard to the design of
    casing strength (including wellbore preparation and running casing) and slurry system. Operation record and logging examination indicate that, by using these design criteria and with primary cementing and plug flow displacement technology, the cement job at Well An-4 has been a success.

    STUDY OF HYDRAULIC BREAKING PROPERTIES OF PETROLEUM ENGINEERING ROCKS
    Xiong Jiyou Liao Rongqing Sun Wentao Ru Dajun
    1999, 21(1):  48-51.  DOI: 10.3863/j.issn.1000-2634.1999.01.012
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    A systematic study was carried out to reveal the internal relationship between physically- and mechanically- different rocks and their jet-breaking behaviors and to establish corresponding quantitative indices. Based on a large number of laboratory tests and theoretical analyses, the petroleum engineering
    rocks are divided into five categories and eleven classes according to their characteristics and physics-mechanics properties. The quantitative relationship is established between different rock types and their jet hydraulic breaking, sing the rock’s compression strength as a quantitative index. It is found that the critical pressure factor of hydraulic breaking ranges from 0.172 to 0.269. Formulas of calculating hydraulic pressure values are presented, and the delayed critical time of rock jet breaking isdetermined experimentally.

    MODEL FOR COMPUTING SURGE AND SWAB PRESSURES IN SLIM AND HORIZONTAL HOLES
    Zhong Bin Shi Taihe Fu Jianhon Miao Shufu
    1999, 21(1):  52-55.  DOI: 10.3863/j.issn.1000-2634.1999.01.013
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    Drilling practice and study show that the surge and swab pressures (SSP) caused by running or pulling a pipe in the wellbore are one of the important causes leading to lost circulation,kicks and other wellbore accidents in the process of oil drilling.So the accurate determination of SSP is the key to controlling pressure balance, preventing possible accidents and thus suc-
    ceeding in balanced drilling. With the increasingly widespread use of slim and horizontal hole (SAHH) drilling technology,new methods of determining SSP are urgently needed. This paper presents a new calculation model, in which the rheology of drilling fluid is described by H-B model, to determine the SSP
    of SAHHs. A comparison between the test data and predicted results indicates that the model is reliable and has a high level of accuracy, and thus can be used in the design and operation of SAHH.

    NEW METHOD OF CALCULATING WELLBORE TEMPERATURE IN GAS WELLS
    Mao Wei Liang Zheng
    1999, 21(1):  56-58(6.  DOI: 10.3863/j.issn.1000-2634.1999.01.014
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    Knowing the temperature distribution in gas well is of great importance to gas well design and dynamic analysis; accurate prediction of wellbore temperature distribution can improve the accuracy of wellbore pressure prediction. Based on energy conservation law, a mathematical model for calculating wellbore
    temperature distribution in a gas well has been developed. This model assumes steady-state heat transfer inside the wellbore and transient heat transfer in the adjacent formation. Data from the literature are used to testify the validity of the model. Results indicate that the temperature distribution predicted by the model agrees well with the measured data.

    STUDY OF SIDE-CUTTING TEST OF ROLLER CONE BIT
    Lin Yulong Hou Jikang
    1999, 21(1):  59-62.  DOI: 10.3863/j.issn.1000-2634.1999.01.015
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    In the drilling operation of deviating and adjusting azimuth for directional and horizontal wells, the function of gage sidecutting of the bit is one of the important factors affecting the rate of penetration and the quality of well profile. In this study,the gage cutters' movement of a tricone bit was simulated, in which the gage cutters' scraping the rock around the wellbore
    and the formation of transition zone were visualized. A testing device was set up and experiments of rock failure by inserts were carried out on selected typical rock samples and by combining various tooth shapes, various cutting structures and different testing parameters. The suffered load on tooth was also analyzed. The result of this study provides technical basis for deter-
    mining gage cutters’shape and designing cutting structure, and has been used with success in the design of the first tricone bitspecial for deviating and adjusting azimuth in China.

    RESEARCH ON THE LUBRICATION MECHANISM OF PLUNGER-SEAL PAIR IN FRACTURING PUMP
    Zhu Weibing Zhou Xirong
    1999, 21(1):  63-66.  DOI: 10.3863/j.issn.1000-2634.1999.01.016
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    Based on the theory of fluid hydraulic lubrication, the plunger-seal pair of fracturing pump in OPI-1800AWS is discussed in detail. The mechanism of film formation under forced lubrication conditions is studied, and the minimum film
    thickness between the plunger and the seal is decided. During the out-let and in-let stroke, the conditions of fluid hydraulic lubrication is met, i.e., there is a parallel film between the plunger and the seal, so the friction is decreased and the lifetime of the plunger-seal pair extended. This suggests that forced
    lubrication plays a key role in the operation of fracturing pumps.

    WELLBORE GAS INFLUX DETECTION BASED ON WAVELET TRANSFORM
    Tang Bin
    1999, 21(1):  67-70.  DOI: 10.3863/j.issn.1000-2634.1999.01.017
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    In this paper, the signal waveform received before and after gas entering the wellbore by transducer placed below the flow return line in the annulus is analyzed. The relationship between the signal waveform suddenness and its wavelet transform is discussed. Based on the analysis of received signal wavelet transform, a novel method of gas influx detection is proposed.
    The validity of the method has been verified by computer simulation.

    化学工程
    EFFECT OF DISSOLVED OXYGEN ON POLYMER STABILITY
    Fu Meilong Zhou Kehou Zhao Lin
    1999, 21(1):  71-73.  DOI: 10.3863/j.issn.1000-2634.1999.01.018
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    The mechanism of HPAM oxidative degradation and the chemical methods of retarding such oxidative degradation are analyzed. The effect of dissolved oxygen on the stability of S725 polymer, as related to the polymer flooding performance in Henan oilfield, is studied. Results show that the viscosity of
    S725 solution prepared with clean water or production water drops rapidly in the presence of oxygen at 65℃. Good viscosity stability can be gained by combination of several additives.

    APPROACH TO THE CHARACTER AND MECHANISM OF POLYELECTROLYTES COMPLEXES AS USED IN DRILLING FLUIDS
    Wang Shaozhong Hu Xingqi
    1999, 21(1):  74-78.  DOI: 10.3863/j.issn.1000-2634.1999.01.019
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    Two cation polyelectrolytes were respectively mixed with two anion polyelectrolytes, and the resultant complexes were examined on their ability to stabilize the wall of well and inhibit swelling of clay. Analyses were made on the compatibility, salt resistance and optimum proportions of the polyelectrolytes in the complexes, with the influence of pH taken into consideration.Results of the tests show that the complexes are highly salt-
    and acid-resistant and are good in properties of inhibiting clay expansion and upholding the properties of drilling fluid. The mechanism of clay-swell inhibition by the complexes is discussed.

    经济管理
    STUDY ON THE COMPREHENSIVE UTILIZATION OFNATURAL GAS PRODUCED IN TUHA OILFIELD
    Deng Lan Tang Xiaodong Wen Fusheng Zhang Bin Yin Daiyi Li Shilun
    1999, 21(1):  79-82.  DOI: 10.3863/j.issn.1000-2634.1999.01.020
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    In order to make full use of the natural gas resources in Tuha oilfield and to improve the oilfield’s economic performance, a research was carried out on the plans of comprehensive utilization of the dry gas, LPG and light oil from the oilfield, in the light of the characteristics and the current status of utiliza-
    tion of the resources. Material balance calculations and economic evaluations were made for each of the potential plans. According to the results it is suggested that the oilfield, with its main activities concentrating on oil and gas exploration and exploitation, can choose certain low-risk and high-profit projects to establish its local natural gas chemical industry, while satisfying
    the need of natural gas consumption of Urumqi City.

    ESTIMATION OF THE ECONOMICALLY RECOVERABLE RESERVE OF AN OILFIELD
    Liu Bin Guo Fujun
    1999, 21(1):  83-87.  DOI: 10.3863/j.issn.1000-2634.1999.01.021
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    In this paper, the authors proposed three methods of calculating the economically recoverable reserve of an oilfield. These methods include: economic limitation method ( limiting water-cut and limiting GOR ), economic recovery method and economic limit well density method. The methods were developed on the basis of analyzing available reserve estimation methods,
    taking into consideration the geological characteristics of Liaohe oilfield and the accounting and taxation system in China. These methods have been used by the authors to calculate the reserves of different pools in the oilfield, and the results have confirmed the methods' validity.
    RELATIONSHIP BETWEEN ORGANIZATIONAL STRUCTURE AND ORGANIZATIONAL FIXED COSTS
    Liu Xianfeng Zhang Mingquan Li Nana
    1999, 21(1):  88-94.  DOI: 10.3863/j.issn.1000-2634.1999.01.022
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    It is well known that fixed costs play an important role in determining the structure of industry. However, it is not as well known the relationship between organizational structure and organizational fixed costs. This paper focuses on such a relationship and presents correspondingly a mathematical model.With this model we are able to determine the size of firms, explain such phenomena as fluctuations in layoff and downsizing of the organization, and explain why the structure of hierarchies of firms is pyramid-shaped. Advantages of using fixed costs to explain the organizational structure are twofold: first, it provides a complementary perspective into organizational structure;second, it provides a link between many seemingly unrelated
    phenomena ( e. g., downsizing and pyramidal hierarchies ).