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Hackley P.C.,U.S. Geological Survey | Zhang L.,Research Institute of Shaanxi Yanchang Petroleum Group | Zhang T.,University of Texas at Austin
Interpretation | Year: 2017

An organic petrology evaluation and a determination of solid bitumen reflectance BRo were completed for organic-rich Triassic Yanchang Formation mudrocks (n=15) from the Ordos Basin, north-central China, as part of a larger investigation of shale gas resources. These data were integrated with information from Rock-Eval programmed pyrolysis to show that the samples are in the peak oil window of thermal maturity and that organic matter is dominated by solid bitumen with minor amounts of type III kerogen (vitrinite and inertinite) from vascular land plants. Describing a kerogen type for these rocks based strictly on parameters determined from programmed pyrolysis is misleading because the original organic matter has converted to hydrocarbons (present as solid bitumen), a large proportion of which may have been expelled into adjacent reservoir facies. However, based on the comparison with immature-early mature lacustrine mudrock (Garden Gulch Member of Green River Formation) and marine shale (Boquillas Formation), we suggest that the original organic matter in the organic-rich samples examined for our study may have been type I/II kerogen with hydrogen index values of >700∈∈mg∈HC/g TOC. © The Authors.

Ji K.,China University of Geosciences | Ji K.,Technical Center | Guo S.,China University of Geosciences | Hou B.,Research Institute of Shaanxi Yanchang Petroleum Group
Journal of Petroleum Science and Engineering | Year: 2017

A large part of shale gas occurs in organic matter and clay mineral surfaces in an adsorption state (20–85%). In a shale reservoir, the pore surfaces of organic matter and clay minerals are the main locations for shale gas adsorption. However, calculating the adsorption gas content is a difficult problem in logging. In order to build a calculation model for adsorption gas, a series of experiments was conducted to understand the relationship between adsorption gas content, mineral type, and content in the Zhaotong Longmaxi formation. These experiments show that organic matter has the most specific surface area and is the most important adsorption matter in the reservoir, especially under low pressure. Clay minerals become more important as the pressure increases. The KIM formula, which is widely used in coalbed methane, was introduced in this work. At a certain temperature and pressure in a reservoir, the gas adsorption specific surface can be simplified as a function of total organic carbon and clay mineral content. The calculated results from the Zhaotong A well are in good agreement with the experiments. The well logging information is used to further calculate the clay minerals of the Zhaotong A well profile, the total organic carbon profile, and the adsorption volume profile. The adsorption gas and total gas of the Zhaotong A well Longmaxi group in a lower place had similar reductions, which is consistent with the field desorption experiment. © 2016 Elsevier B.V.

Wang X.-Z.,Shaanxi Yanchang Petroleum Group Co. | Fan B.-J.,Research Institute of Shaanxi Yanchang Petroleum Group
Natural Gas Geoscience | Year: 2016

Lacustrine shale is well developed in the Shanbei area, and some shale gas wells have been put into production in this area. However, the researches on shale gas migration as well as storage process are very poor, the estimation about shale gas reserves is also a debatable issue for exploration. Solving the above challenges helps to recognize the resource potential, and reduce exploration risk. The gas components and carbon isotope compositions can be obtained from the desorbing experiments, and these data provide us with important information about the origins and storage process of shale gas. Furthermore, they can help to solve the problems of geological mechanisms and reserves calculations. The results show that, the shale gas in the study area is oil type gas; the heavy gases as well as methane enriched in 13C have the priority over other components to absorb on the shale surface; the small molecules have the priority over large molecules to migrate within the shale; the formation order of different gas types is absorbing gas, dissolving gas and then free gas. © 2016, Science Press. All right reserved.

Sun X.,Research Institute of Shaanxi Yanchang Petroleum Group | Liang X.,Research Institute of Shaanxi Yanchang Petroleum Group | Wang S.,Xi'an Jiaotong University | Lu Y.,Xi'an Jiaotong University
Journal of Petroleum Science and Engineering | Year: 2014

Foam provides a highly attractive alternative to conventional non-Newtonian fluids for various oil and gas fracturing applications because of high viscosity and low liquid loss. However, much work has been carried out under 7MPa, a pressure much less than that of the practical fracturing value. In this paper, the rheology of CO2 viscoelastic surfactant foam fracturing fluid was investigated under downhole condition on a large scale flow-loop experiment system. The testing results show that the foam fluid is shear thinning and its rheological properties can be described by the power-law model. Besides, the character of the fluid is different greatly from that of single phase non-Newtonian fluid because of its formation of foam and structure of external phase. It was also found that the viscosity of CO2 viscoelastic surfactant foam fracturing fluid was proportional to the increment of foam quality and pressure, which, however, was inversely proportional to the increase of temperature and shear rate. Moreover, through analysis of the effects of different factors on the rheology characteristics, the correlations of rheological parameters, as well as the relation of frictional resistance coefficient λ versus generalized Reynolds number R e, were obtained. © 2014 Elsevier B.V.

Wang X.,Shaanxi Yanchang Petroleum Group Co. | Wu J.,Research Institute of Shaanxi Yanchang Petroleum Group | Zhang J.,Research Institute of Shaanxi Yanchang Petroleum Group
Natural Gas Industry | Year: 2014

China boasts of abundant terrestrial shale gas resources. Compared with marine shale, terrestrial shale has smaller thickness, lower content of brittle minerals, higher content of clay minerals, and lower pressure. Hence, the development technology for marine shale gas, especially the fracturing technology, is not entirely applicable to terrestrial shale. To this end, aimed at the reservoir characteristics and fracturing difficulties, the features of liquid CO2 foam and CO2 energized fracturing technology were analyzed, and their application tests were carried out in the gas shale in the Chang-7 Member of Mesozoic Yangchang Fm in the Ordos Basin. The application results showed that pure liquid CO2 at a discharge rate of 2.0 m3/min was capable of fracturing shale gas reservoirs in Chang-7 Member with a rapid liquid unloading, and ignition could be conducted after 24 h. Meanwhile, CO2 energized fracturing greatly improved the fracturing fluid flowback speed and rate to shorten the liquid unloading period, which all benefited the terrestrial shale gas exploration and development. Moreover, based on the analysis of the state-of-the-art of fracturing technologies and facilities in China, the application prospect and development idea were presented of the CO2 fracturing technology applied in terrestrial shale gas development.

Ge X.,China University of Petroleum - East China | Fan Y.,China University of Petroleum - East China | Cao Y.,China University of Petroleum - East China | Xu Y.,China University of Petroleum - East China | And 2 more authors.
Applied Magnetic Resonance | Year: 2014

The carbonate reservoir has a number of properties such as multi-type pore space, strong heterogeneity, and complex pore structure, which make the classification of reservoir pore structure extremely difficult. According to nuclear magnetic resonance (NMR) T2spectrum characteristics of carbonate rock, an automatic pore structure classification and discrimination method based on the T2spectrum decomposition is proposed. The objective function is constructed based on the multi-variate Gaussian distribution properties of the NMR T2 spectrum. The particle swarm optimization algorithm was used to solve the objective function and get the initial values and then the generalized reduced gradient algorithm was proposed for solving the objective function, which ensured the stability and convergence of the solution. Based on the featured parameters of the Gaussian function such as normalized weights, spectrum peaks and standard deviations, the combi-natory spectrum parameters (by multiplying peak value and normalized weight for every peak) are constructed. According to the principle of fuzzy clustering, the carbonate rock pore structure is classified automatically and the discrimination function of each pore structure type is obtained using Fisher discrimination analysis. The classification results were analyzed with the corresponding casting thin section and scanning electron microscopy. The study shows that the type of the pore structure based on the NMR T2 spectrum decomposition is strongly consistent with other methods, which provides a good basis for the quantitative characterization of the carbonate rock reservoir pore space and lays a foundation of the carbonate rock reservoir classification based on NMR logging. © Springer-Verlag Wien 2014.

Cui M.-W.,China University of Petroleum - East China | Cao X.-W.,China University of Petroleum - East China | Feng Z.-Y.,Research Institute of Shaanxi Yanchang Petroleum Group
Chuan Bo Li Xue/Journal of Ship Mechanics | Year: 2014

The failure pressure of oil and gas pipeline with different morphology of corrosion pits was analysed by using the nonlinear finite element method. The impact of the cross-section area of corrosion pit on pipeline failure pressure with the axial and circumferential corrosion was researched. The analysis showed that the cross-section area of corrosion pits seriously influenced the failure pressure of pipeline with axial corrosion, however, which was not enough to fully describe the effects of the morphology of corrosion pits on pipeline failure pressure. The research considered the effects of the morphology of corrosion pits by using the cross-section area of corrosion pit and form factor of corrosion pit to descripe on pipeline failure pressure, and proposed a new B31G correction formula. The results show that forecast error and the fluctuation range of the error are little using the formula.

Huang H.,Research Institute of Shaanxi Yanchang Petroleum Group
Advanced Materials Research | Year: 2013

For the purpose of inclination measurement and monitoring, a tilt angle measurement system using a heat convection accelerometer is presented in this study. A conditioning circuit that center around the single chip processor is designed and built. Experiments were carried out to characterize the measuring system with the range of -90° to +90°. The output results show nonlinear relationship. The calibration result indicates that the sensitivity of the accelerometer is about 650mV/g. The maximum error is 5.5% while the repeatability error is 3%. Experiments proved that the developed measurement system is capable of measuring tilt angle. © (2013) Trans Tech Publications, Switzerland.

Tao H.S.,Research Institute of Shaanxi Yanchang Petroleum Group | Sun X.,Research Institute of Shaanxi Yanchang Petroleum Group
Advanced Materials Research | Year: 2014

In CO2 foam flooding progress, foams formed by CO2 and surfactant solution can reduce the fluidity of CO2, improve sweep efficiency and flow behavior of CO2 in heterogeneous oil reservoir, prevent fingering and channeling and improve recovery efficiency. However, the study on the CO2 foam flooding characteristics is still in the initial stage, this paper focused on experimental testing the CO2 foam fluid flooding characteristics. Factors affecting the foam flooding efficiency, such as surfactant concentration, foam quality, injection method and core permeability, were studied in more detail in the paper, and influencing laws of factors on flooding efficiency and recovery efficiency were analyzed, moreover, based on experiments, the optimum foam quality and injection method, which have a practical and theoretical significance to the engineering application, were obtained. © (2014) Trans Tech Publications, Switzerland.

Yu B.,Research Institute of Shaanxi Yanchang Petroleum Group
Northwestern Geology | Year: 2016

In east-southern Ordos basin, the Styles of third-order sequence boundary in Upper Pa-leozoic strata within can be districted as seven styles, including regional unconformity, structural system transformation surface, regional regression surface, channel erosion surface, regional leakage surface, coal bed, overlay-style transformation surface between limestone bottom and strata. Based on the analysis of sequence boundary characteristic, the Paleozoic stratigraphy, from Benxi Formation to Shihezi Formation, can be divided into two second-order sequences, namely the one (SSI) includes Benxi Formation, Taiyuan Formation and Shanxi Formation, the other (SS2) includes Shihezi Formation. Every second-order sequence is dominated by tectonic, including regional transgression and regression cycles. The second-order sequence can be divided into 11 third-order sequences, that is two third-order sequences CSQ1 and SQ2) in Benxi Formation, one (SQ3) in Taiyuan Formation, two (SQ4 and SQ5) in Shanxi Formation, six (SQ6 and SQ11) in Shihezi Formation. In which, the sequences of SQ1-SQ5 are marine and marine-conti-nental sediments, while SQ6-SQ11 are lacustrine sediments on continental. With the characteristic of sequence stratigraphy, the sequence-filling model in east-southern Ordos Basin has been established in this paper, which has a guiding significance for further research in sedimentary system evolution, reservoir formation and gathering for gas.

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