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Experimental investigation of shale imbibition capacity and the factors influencing loss of hydraulic fracturing fluids

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petroleum Science 2015年第4期12卷 636-650页

作者： Hong-Kui Ge Liu Yang Ying-Hao Shen Kai Ren Fan-Bao Meng Wen-Ming Ji Shan Wu state key laboratory of petroleum resources and prospecting China University of Petroleum

Spontaneous imbibition of water-based frac- turing fluids into the shale matrix is considered to be the main mechanism responsible for the high volume of water loss during the flowback period. Understanding the matrix imbibition capacity and rate helps to determine the frac- turing fluid volume, optimize the flowback design, and to analyze the influences on the production of shale gas. Imbibition experiments were conducted on shale samples from the Sichuan Basin, and some tight sandstone samples from the Ordos Basin. Tight volcanic samples from the Songliao Basin were also investigated for comparison. The effects of porosity, clay minerals, surfactants, and KC1 solutions on the matrix imbibition capacity and rate were systematically investigated. The results show that the imbibition characteristic of tight rocks can be characterized by the imbibition curve shape, the imbibition capacity, the imbibition rate, and the diffusion rate. The driving forces of water imbibition are the capillary pressure and the clay absorption force. For the tight rocks with low clay contents, the imbibition capacity and rate are positively correlated with the porosity. For tight rocks with high clay content, the type and content of clay minerals are the most impor- tant factors affecting the imbibition capacity. The imbibed water volume normalized by the porosity increases with an increasing total clay content. Smectite and illite/smectite tend to greatly enhance the water imbibition capacity. Furthermore, clay-rich tight rocks can imbibe a volume of water greater than their measured pore volume. The aver- age ratio of the imbibed water volume to the pore volume is approximately 1.1 in the Niutitang shale, 1.9 in the Lujiaping shale, 2.8 in the Longmaxi shale, and 4.0 in the Yingcheng volcanic rock, and this ratio can be regarded as a parameter that indicates the influence of clay. In addition, surfactants can change the imbibition capacity due to alteration of the capillary pressure and

关键词： Imbibition . Shale Fracturing fluid Capillary pressure Clay

Geochemical studies of the Silurian oil reservoir in the Well Shun-9 prospect area, Tarim Basin, NW China

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petroleum Science 2013年第4期10卷 432-441页

作者： Song Daofu Li Meijun Wang T.–G state key laboratory of petroleum resources and prospecting China University of Petroleum

Commercial oil flow has been obtained from the sandstone reservoir of the Lower Silurian Kelpintag Formation in the Well Shun-9 prospect *** the present studies,10 Silurian oil and oil sand samples from six wells in the area were analyzed for their molecular and carbon isotopic compositions,oil alteration（biodegradation）,oil source rock correlation and oil reservoir filling *** the Silurian oils and oil sands are characterized by low Pr/Ph and C21/C23 tricyclic terpane（〈1.0） ratios,＂V＂-pattern C27-C29 steranes distribution,low C28-sterane and triaromatic dinosterane abundances and light δ13C values,which can be correlated well with the carbonate source rock of the O3 l Lianglitage *** oil biodegradation levels have also been confirmed for the different oils/oil sands *** the S1k2 seal,oils and oil sands from the S1k1 interval of the Kelpintag Formation have only suffered light biodegradation as confirmed by the presence of ＂UCM＂ and absence of 25-norhopanes,whereas the S1k3-1 oil sands were heavily biodegraded（proved by the presence of 25-norhopanes） due to the lack of the S1k2 seal,which suggests a significant role of the S1k2 seal in the protection of the Silurian oil *** on the Ts/（Ts＋Tm） and 4-/1-MDBT ratios as reservoir filling tracers,a general oil filling direction from NW to SE has been also estimated for the Silurian oil reservoir in the Well Shun-9 prospect area.

关键词： Silurian oil reservoir Well Shun-9 prospect area geochemistry oil source rock correlation alteration oil reservoir filing direction

Properties and testing of a hydraulic pulse jet and its application in offshore drilling

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petroleum Science 2014年第3期11卷 401-407页

作者： Shi Huaizhong Li Gensheng Huang Zhongwei Shi Shuaishuai state key laboratory of petroleum resources and prospecting China University of Petroleum

Offshore drilling has attracted more attention than ever before due to the increasing worldwide energy demand especially in China. High cost, long drilling cycles, and low rate of penetration （ROP） represent critical challenges for offshore drilling operations. The hydraulic pulse generator was specifically designed, based on China offshore drilling technologies and parameters, to overcome problems encountered during offshore drilling. Both laboratory and field tests were conducted to collect the characteristics of the hydraulic pulse generator. The relationships between flow rate and pressure amplitude, pressure loss and pulse frequency were obtained, which can be used to optimize operation parameters for hydraulic pulse jet drilling. Meanwhile a bottom hole assembly （BHA） for pulse jet drilling has been designed, combining the hydraulic pulse generator with the conventional BHA, positive displacement motor, and rotary steerable system （RSS） etc. Furthermore, the hydraulic pulse jet technique has been successfully applied in more than 10 offshore wells in China. The depth of the applied wells ranged from 2,000 m to 4,100 m with drilling bit diameters of 311 mm and 216 mm. The field application results showed that hydraulic pulse jet technique was feasible for various bit types and formations, and that ROP could be significantly increased, by more than 25%.

关键词： Pulse jet offshore drilling parameter test oilfield application rate of penetration

Petrology and geochemistry of the Carboniferous cutinite-rich coals from the Hequ area of Shanxi Province, China

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Science China Earth Sciences 2022年第10期65卷 2018-2032页

作者： Daofu SONG Tieguan WANG Ping LI Jiadong YAN Xiangji ZHENG state key laboratory of petroleum resources and prospecting China University of PetroleumBeijing 102249China

Coal samples taken from the Taiyuan Formation in the Hequ area, China, for this study are typical cutinite-rich *** petrology and geochemistry of the samples were analyzed using microscopic examination, proximate and ultimate analysis,rock pyrolysis, and gas chromatography-mass spectrometry(GC-MS). The cutinites in Haochuan(HC) coals are predominantly of the thin-walled type, whereas those in the Jingzigou(JZG) coals are predominantly thick-walled. The variable thickness of cutinites in different coals is related to the environment in which the coal-forming plants grew. Compared with typical Ⅲ kerogens, HC and JZG bituminous coals are characterized by high volatile matter yields and hydrogen contents due to the elevated hydrogen-rich cutinite content. Pyrolysis data indicate that these cutinite-rich coals can be expected to generate commercial liquid and gaseous hydrocarbons. Pristane(Pr) and phytane(Ph) are both abundant in the samples, with the Pr/Ph ratios for both the HC and JZG coals being >3.0, indicating moderate maturity and oxic peat depositional conditions. The C>>C>Cnormalized relative abundance of regular steranes is consistent with a dominant contribution from higher *** hopanes in the coals also suggest a substantial organic matter input from bacteria, which are common inhabitants of peat and coal. Palynology studies indicate that pteridophytes are likely to be the most common coal-forming plants. A gymnosperm contribution is also indicated by the presence of tetracyclic diterpenes. Massive accumulations of cuticles as cutinite in coal are rare and account for only a small proportion of coals worldwide. However, cutinite-rich coals are found in the northern margin of the North China Craton, in the Taiyuan Formation. The accumulation of cutinite in this area is the result of distinctive peat deposition conditions. Frequent marine transgression was an important contributing factor.

关键词： Cutinite-rich coal Carboniferous Coal petrology Geochemistry Hequ area

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Petrology and organic geochemistry of the Baishaping and Damaidi Devonian cutinitic liptobioliths,west of the Kangdian Uplift,China

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petroleum Science 2022年第5期19卷 1978-1992页

作者： Dao-Fu Song Tie-Guan Wang Ping Li Mai Zhang An-Liang Liu Jia-Dong Yan state key laboratory of petroleum resources and prospecting China University of PetroleumBeijing 102249China

Devonian cutinitic liptobiolith is a special type of coal formed during the early evolutionary stage of land *** Baishaping and Damaidi Devonian coals are notable for their distinct papery,sheet-like texture,and unusually high cutinite content(>50%),belonging to typical cutinitic *** are bituminous coals and have a suppressed vitrinite *** with typical typeⅢkerogen,these liptobioliths are characterized by extremely high yields of volatile matter and high hydrogen contents owing to their enhanced cutinite *** indicated by pyrolysis and elemental analysis results,the Devonian cutinitic liptobioliths are dominated by typeⅠ-Ⅱkerogens and have an excellent potential to generate liquid *** Baishaping cutinitic liptobioliths are mainly composed of ribbon-like thick-walled cutinites,with small amounts of thin-walled *** is only present in trace amounts and is dominated by ***,the Damaidi Devonian coals are primarily composed of ribbon-like thin-walled cutinites,followed by collotelinites which are usually sandwiched by *** different petrological characteristics of the Baishaping and Damaidi liptobioliths might indicate a structural variation in the coal-forming plant cuticles and two distinct coal-forming *** molecular bio markers in the Devonian coals are mainly composed of C_(18)-C_(20)tetracyclic diterpenoids,which are assumed to be the dominant soluble constituent of the Devonian land-plant cuticles and might have played an important role in early land plant *** molecules include aromatic tetracyclic diterpenoids,3-5 ring polycyclic aromatic hydrocarbons and their methylated counterparts,and C_(16)-and C_(18)-monocarboxylic acids.n-Alkanes are present only in small *** molecular composition of the cutinite-rich coals is unexpected,because cuticular waxes are one of the most important sources of *** general,the petrology and geochemistry

关键词： Coal chemistry Macerals Hydrocarbon potential Plant cuticles Tetracyclic diterpenoids

Settling behavior of non-spherical particles in power-law fluids:Experimental study and model development

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Particuology 2019年第5期17卷 30-39页

作者： Zhengming Xu Xianzhi Song Gensheng Li Zhaoyu Pang Zhaopeng Zhu state key laboratory of petroleum resources and prospecting China University of Petroleum Beijing 102249 China

Solid-particle settling occurs in many natural and industrial processes, such as in the transportation of drilling cuttings and fracturing proppant. Knowledge of the drag coefficient and settling velocity of cuttings and proppant is of significance to hydraulics design, wellbore cleanout, and fracture optimization. We conducted 553 tests to investigate the settling characteristics of spherical and non-spherical particles in power-law fluids. Three major particle shapes (spherical, cubic, and cylindrical) and eight different particle sphericities were used to simulate cuttings and proppant, and power-law fluids were applied to simulate drilling and fracturing fluids. Based on the data analysis, a new drag coefficient-particle Reynolds number correlation was developed to determine the drag coefficient in a power-law fluid for spherical and non-spherical particles. The drag coefficient increases as the sphericity decreases for the same particle Reynolds number. For a specific particle shape, the drag coefficient decreases as the particle Reynolds number increases, but the decreasing trend is reduced at high particle Reynolds number conditions. An explicit settling-velocity equation was proposed to calculate the settling velocity of spherical and non-spherical particles in power-law fluids by considering the effect of sphericity. A suitable range for the proposed model is 0.0001 < Re <200, 0.471 <φ< 1, and 0.505 < n < 1. An illustrative example is presented to show how to calculate the drag coefficient and settling velocity in power-law fluids with given particle and fluid properties.

关键词： Settling velocity Drag coefficient Non-spherical particle Spherical particle Power-law fluids

Experimental study of the azimuthal performance of 3D acoustic transmitter stations

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petroleum Science 2016年第1期13卷 52-63页

作者： Xiao-Hua Che Wen-Xiao Qiao Xiao-Dong Ju Jun-Qiang Lu Jin-Ping Wu Ming Cai state key laboratory of petroleum resources and prospecting China University of Petroleum key laboratory of Earth prospecting and Information Technology China University of Petroleum

Better well logging techniques for geologic investigations are urgently needed to identify and evaluate complex *** describe a new type of 3D transmitter station with corresponding circuits and *** can be used in a promising new technique of acoustic reflection well logging,that features better azimuthal detection capabilities,as well as better investigation *** transmitter stations consist of three-level subarrays that can radiate acoustic energy in any required azimuth of 3D space by circularly exciting various combinations at different *** tested the 3D acoustic transmitter stations and obtained laboratory directivity measurements with the3 D acoustic transmitter stations for the first *** results show that the 3-d B beam width in the horizontal plane ranges from 59° to 67° as a result of phase-delayed *** main beam is steered in the vertical plane at a deflection angle that ranges from 0° to 16° when the delay time of the excitation pulse between each pair of adjacent arc arrays is gradually *** 3-d B beam width is equal to 11°,whereas the deflection angle in the vertical plane is equal to 14°.Each of the four third-level subarrays in the same circumferential direction display consistent horizontal and vertical directivities,thus satisfying the requirements of azimuthal acoustic reflection logging.

关键词： transmitter deflection logging urgently geologic satisfying azimuth exciting excitation formations

Analytical method for evaluating stress field in casing-cement-formation system of oil/gas wells

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Applied Mathematics and Mechanics(English Edition) 2017年第9期38卷 1273-1294页

作者： Wei LIU Baohua YU Jingen DENG state key laboratory of petroleum resources and prospecting China University of PetroleumBeijing 102249China

In this paper, we present an analytical method for evaluating the stress field within a casing-cement-formation system of oil/gas wells under anisotropic in-situ stresses in the rock formation and uniform pressure within the casing. The present method treats the in-situ stresses in the formation as initial stresses since the in-situ stresses have already developed in the formation before placement of cement and casing into the well. It is demonstrated that, via this treatment, the present method excludes additional displacements within the formation predicted by the existing method, and gives more reasonable stress results. An actual tight-oil well is analyzed using the present and existing analytical methods, as well as the finite element method. Good agreement between the analytical results and the finite element analysis （FEA） results is obtained, validating the present method. It is also evident that, compared with the present method, the existing method overestimates the compressive stress level within the casing and the cement. Finally, the effects of elastic properties of the formation, cement, and inner pressure of casing on stresses within the casing and cement are illustrated with a series of sensitivity analyses.

关键词： near wellbore region stress evaluation anisotropic in-situ stress initialstress

Productivity enhancement in multilayered coalbed methane reservoirs by radial borehole fracturing

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petroleum Science 2022年第6期19卷 2844-2866页

作者： Rui-Yue Yang Gen-Sheng Li Xiao-Zhou Qin Zhong-Wei Huang Jing-Bin Li Mao Sheng Bin Wang state key laboratory of petroleum resources and prospecting China University of PetroleumBeijing102249China

Coalbed methane(CBM)is an important unconventional natural *** of multilayered CBM reservoir is still facing the challenge of low production *** borehole fracturing,which integrates radial jet drilling and hydraulic fracturing,is expected to create complex fracture networks in multilayers and enhance CBM *** main purpose of this paper is to investigate the mechanisms and efficacy of radial borehole fracturing in increasing CBM production in multiple ***,a two-phase flow and multi-scale 3 D fracture network including radial laterals,hydraulic fractures and face/butt cleats model is established,and embedded discrete fracture model(EDFM)is applied to handle the complex fracture ***,effects of natural-fracture nonuniform distribution are investigated to show the advantages of targeted stimulation for radial borehole ***,two field CBM wells located in eastern Yunnan-western Guizhou,China were presented to illuminate the stimulation efficiency by radial borehole *** results indicated that compared with vertical well fracturing,radial borehole fracturing can achieve higher gas/water daily production rate and cumulative gas/water production,approximately 2 times *** communications to cleats and sweet spots and flexibility in designing radial borehole parameters in different layers so as to increase fracture-network complexity and connectivity are the major reasons for production enhancement of radial borehole ***,the integration of geology-engineering is vital for the decision of radial borehole fracturing designing *** key findings of this paper could provide useful insights towards understanding the capability of radial borehole fracturing in developing CBM and coal-measure gas in multiple-thin layers.

关键词： Coalbed methane Multilayered coal beds Radial borehole fracturing Complex fracture networks Cleats distribution