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Neutron and density logging responses to gas reservoir for well-balanced and under-balanced logging:Gas reservoirs of sandstone in a western china field

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Science china Earth Sciences 2008年第S2期51卷 201-206页

作者： WU WenSheng1,XIAO LiZhi1 & ZHANG LongHai2 1 Resource & Information department,china university of petroleum,beijing 102249,china 2 Research Institute of petroleum Exploration and Development,Petrochina,beijing 100083,china Resource & Information department China University of Petroleum Beijing China Research Institute of petroleum Exploration and Development PetroChina Beijing China

Studying the response differences between neutron and density logging of gas reservoir for well-balanced and under-balanced logging will be of significance in evaluation of gas reservoir under the under-balanced condition and application of logging data. With Monte Carlo simulation technique,the paper obtains the relationship between neutron and density logging measurement and borehole di-ameter,porosity or gas saturation for well-balanced and under-balanced logging. The conclusions show that the response trend of under-balanced logging to gas reservoirs agrees with that of well-balanced logging with small borehole,and under-balanced logging data can be used usually as well-balanced logging data. When borehole diameter is large,under-balanced logging data should be corrected for the influences of borehole.

关键词： under-balanced logging density logging neutron logging gas reservoir response

Anisotropic characteristics of electrical responses of fractured reservoir with multiple sets of fractures

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petroleum Science 2009年第2期6卷 127-138页

作者： Shen Jinsong Su Benyu Guo Naichuan department of Geophysics School of Resource and Information Technology China University of Petroleum Beijing 102249 China Key Laboratory of CNPC Geophysical Exploration China University of Petroleum Beijing 102249 China State Key Laboratory of petroleum Resource and Prospecting China University of Petroleum Beijing 102249 China

In fractured reservoirs, the fractures not but also form the main flow channels which connect productivity of reservoirs. However, because of the only provide the storage space for hydrocarbons, the pores of the matrix, so fractures dominate the heterogeneity and randomness of the distribution of fractures, exploration and evaluation of fractured reservoirs is still one of the most difficult problems in the oil industry. In recent years, seismic anisotropy has been applied to the assessment of fractured formations, whereas electrical anisotropy which is more intense in fractured formations than seismic anisotropy has not been studied or used so extensively. In this study, fractured reservoir models which considered multiple sets of fractures with smooth and partly closed, rough surfaces were established based on the fractures and pore network, and the vertical and horizontal electrical resistivities were derived as a function of the matrix and fracture porosities according to Ohm＇s law. By using the anisotropic resistivity equations, variations of the electrical anisotropy of three types of fractured models under the conditions of free pressure and confining pressure were analyzed through the variations of the exerted pressure, matrix porosity, fracture aperture and formation water resistivity. The differences of the vertical and horizontal resistivities and the anisotropy between the connected and non-connected fractures were also analyzed. It is known from the simulated results that an increase of the confining pressure causes a decrease of electrical anisotropy because of the elasticity of the closed fractures and the decrease of the fracture aperture. For a fixed fracture porosity, the higher the matrix porosity, the weaker the electrical anisotropy in the rock formation.

关键词： Fractured reservoir partly closed fracture electrical anisotropy fracture roughness

Identification Algorithm Based on the Approximate Least Absolute Deviation Criteria

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International Journal of Automation and computing 2012年第5期9卷 501-505页

作者： Bao-Chang Xu Xin-Le Liu department of Automation, china university of petroleum, beijing 102249, china department of Automation China University of Petroleum Beijing China

Considering the situation that the least-squares (LS) method for system identification has poor robustness and the least absolute deviation (LAD) algorithm is hard to construct, an approximate least absolute deviation (ALAD) algorithm is proposed in this paper. The objective function of ALAD is constructed by introducing a deterministic function to approximate the absolute value function. Based on the function, the recursive equations for parameter identification are derived using Gauss-Newton iterative algorithm without any simplification. This algorithm has advantages of simple calculation and easy implementation, and it has second order convergence speed. Compared with the LS method, the new algorithm has better robustness when disorder and peak noises exist in the measured data. Simulation results show the efficiency of the proposed method.

关键词： System identification least absolute deviation (LAD) Gauss-Newton algorithm robustness disorder and peak noise

Effects of abnormally high heat stress on petroleum in reservoir——An example from the Tazhong 18 Well in the Tarim Basin

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Science china Earth Sciences 2008年第4期51卷 515-527页

作者： ZHU DongYa1, JIN ZhiJun1, HU WenXuan2 & ZHANG XueFeng3 1 petroleum Exploration and Production Institute, china petroleum & Chemical Corporation, beijing 100083, china 2 department of Earth Sciences, Nanjing university, Nanjing 210093, china 3 School of Resource and Information, china university of petroleum, beijing 102249, china petroleum Exploration and Production Institute China Petroleum & Chemical Corporation Beijing China department of Earth Sciences Nanjing University Nanjing China School of Resource and Information China University of Petroleum Beijing China

An igneous intrusion of 94m thick was discovered intruding into the Silurian sandstone from Tazhong 18 Well. The petroleum previously preserved in the Silurian sandstone reservoir was altered into black carbonaceous bitumen by abnormally high heat stress induced by the igneous intrusion. The reflec-tance of the carbonaceous bitumen reaches as high as 3.54%, indicating that the bitumen had evolved into a high thermal evolution level. Similar to the Silurian samples from the neighboring Tazhong 11, Tazhong 12, Tazhong 45 and Tazhong 47 wells, the distribution of C27, C28 and C29 steranes of the car-bonaceous bitumen is still "V" -shaped and can still be employed as an efficient parameter in oil source correlation. The "V" -shaped distribution indicates that the hydrocarbons from the Tazhong 18 and the neighboring wells were all generated from the Middle-Upper Ordovician hydrocarbon source rocks. However, the oil source correlation parameters associated with and terpanes had been changed greatly by the high heat stress and can no longer be used in oil source correlation. The δ 13C values of the pe-troleum from the neighboring wells are between -32.53‰ and -33.37‰, coincident with those of the Paleozoic marine petroleum in the Tarim Basin. However, the δ 13C values of the carbonaceous bitumen from the Tazhong 18 Well are between -27.18‰ and -29.26‰, isotopically much heavier than the pe-troleum from the neighboring wells. The content of light hydrocarbons (nC14-nC20) of the saturated hydrocarbon fraction in the carbonaceous bitumen is extremely higher than the content of heavy hy-drocarbons. The light/heavy hydrocarbon ratios (ΣnC21-/ΣnC22+) are between 4.56 and 39.17. In the saturated fraction, the even numbered hydrocarbons are predominant to the odd numbered, and the OEP (Odd to Even Predominance) values are between 0.22 and 0.49. However, the content of light hy-drocarbons in the petroleum from the neighboring wells is relatively low and the content of the even numb

关键词： Tarim Basin igneous intrusive abnormally high heat stress bitumen carbon isotope PAH

Particle tunnels across the horizon of Garfinkle-Horowitz-Strominger dilaton black hole

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Science china(Physics,Mechanics & Astronomy) 2007年第5期50卷 601-610页

作者： FANG HengZhong1 & ZHAO Zheng2 1 department of Physics, china university of petroleum, Dongying 257061, china 2 department of Physics, beijing Normal university, beijing 100875, china department of Physics China University of Petroleum Dongying China department of Physics Beijing Normal University Beijing China

We promote the work of Parikh and Wilczek on the black hole radiation to the emission of massive and charged particles from Garfinkle-Horowitz-Strominger black hole. The energy and charge of the space-time are conservational during the course of the evaporation. The calculation shows that the emission spectrum is not precisely thermal, while has a correction, and the conclusion supports the view- point of information conservation.

关键词： Hawking radiation, black body spectrum, barrier, information loss, entropy of black hole, Komar energy

Structural characteristics of the Tan-Lu fault zone in Cenozoic basins offshore the Bohai Sea

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Science china Earth Sciences 2008年第S2期51卷 20-31页

作者： QI JiaFu1,2,ZHOU XinHuai3,DENG RongJing4 & ZHANG KeXin2 1 State Key Laboratory of petroleum Resource and Prospecting,china petroleum university,beijing 102249,china 2 department of Earth Sciences,china petroleum university,beijing 102200,china 3 Tianjin Branch of CNOOC china Limited,Tianjin 300451,china 4 beijing Research Center of CNOOC china Limited,beijing100027,china State Key Laboratory of petroleum Resource and Prospecting China Petroleum University Beijing China department of Earth Sciences China Petroleum University Beijing China Tianjin Branch of CNOOC china Limited Tianjin China beijing Research Center of CNOOC china Limited Beijing China

The Tan-Lu fault zone across the eastern margin of the Cenozoic basins offshore the Bohai Sea is a NNE-trending right-lateral strike-slip fault system developed in the Cenozoic basin cover. It cuts through NE-to NNE-striking major extensional faults that controlled the formation of Paleogene basins. Recent petroleum exploration indicates that Cenozoic structural activities of the Tan-Lu fault system have directly or indirectly affected oil and gas distribution offshore the Bohai Sea. As part of a deep fault zone the Tan-Lu fault zone has been activated since the Oligocene,and obviously affected the tectonic evolution of offshore Bohai basins since then. The formation of Paleogene rift basins offshore the Bohai Sea has utilized the pre-existing structural elements of the Tan-Lu fault zone that developed in the late Mesozoic.

关键词： strike-slip fault extensional structure Tan-Lu fault zone Bohaiwan basin

2.5-D modeling of cross-hole electromagnetic measurement by nite element method

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petroleum Science 2008年第2期5卷 126-134页

作者： Shen Jinsong Sun Wenbo department of Geophysics School of Resources and Information Technology China University of Petroleum Beijing 102249 China CNPC Key Lab of Geophysical Exploration China University of Petroleum Beijing 102249 China

A finite element method is developed for simulating frequency domain electromagnetic responses due to a dipole source in the 2-D conductive structures. Computing costs are considerably minimized by reducing the full three-dimensional problem to a series of two-dimensional problems. This is accomplished by transforming the problem into y-wave number （Ky） domain using Fourier transform and the y-axis is parallel to the structural strike. In the Ky domain, two coupled partial differential equations for magnetic field Hy and electric field Ey are derived. For a specific value of Ky, the coupled equations are solved by the finite element method with isoparametric elements in the x-z plane. Application of the inverse Fourier transform to the Ky, domain provides the electric and magnetic fields in real space. The equations derived can be applied to general complex two-dimensional structures containing either electric or magnetic dipole source in any direction. In the modeling of the electromagnetic measurement, we adopted a pseudo-delta function to distribute the dipole source current and circumvent the problem of singularity at the source point. Moreover, the suggested method used isoparametric finite elements to accommodate the complex subsurface formation. For the large scale linear system derived from the discretization of the Maxwell＇s equations, several iterative solvers were used and compared to select the optimal one. A quantitative test of accuracy was presented which compared the finite element results with analytic solutions for a dipole source in homogeneous space for different ranges and different wave numbers Ky. to validate the addressed the effects of the distribution range τ of the homogeneous medium. code and check its effectiveness. In addition, we pseudo-delta function on the numerical results in

关键词： 2.5-D electromagnetic modeling frequency domain isoparametric finite element pseudo-delta function

Geophysical methods for the study of sedimentary cycles

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petroleum Science 2009年第3期6卷 259-265页

作者： Xu Jingling Liu Luofu Wang Guiwen Shen Jinsong Zhang Chunhua School of Resources and Information Technology China University of Petroleum Beijing 102249 China State Key Laboratory of petroleum Resource and Prospecting China University of Petroleum Beijing 102249 China department of Computer Science and Technology China University of Petroleum Beijing 102249 China

We present the wavelet depth-frequency analysis and variable-scale frequency cycle analysis methods to study sedimentary cycles. The spectrum analysis, variable-scale frequency cycle analysis, and wavelet depth-frequency analysis methods are mainly discussed to distinguish sedimentary cycles of different levels. The spectrum analysis method established the relationship between the spectrum characteristics and the thickness and number of sedimentary cycles. Both the variable-scale frequency cycle analysis and the wavelet depth-frequency analysis are based on the wavelet transform. The variable-scale frequency cycle analysis is used to obtain the relationship between the periodic changes of frequency in different scales and sedimentary cycles, and the wavelet depth-frequency analysis is used to obtain the relationship between migration changes of frequency energy clusters and sedimentary cycles. We designed a soft-ware system to process actual logging data from the Changqing Oilfield to analyze the sedimentary cycles, which verified the effectiveness of the three methods, and good results were obtained.

关键词： Sedimentary cycles spectrum analysis wavelet depth-frequency analysis variable-scale frequency cycle analysis

Composition of substituents on pyrrole ring of high-carbon-number geoporphyrins and its dealkylation

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Chinese Science Bulletin 1999年第3期44卷 267-269页

作者： ZHANG Chunming and LIN Renzi Geochemistry Research Center, Jianghan petroleum Institute, Jingzhou 434102, china department of geoscience, university of petroleum , beijing 100083, china Geochemistry Research Center Jianghan Petroleum Institute Jingzhou China department of geoscience University of Petroleum Beijing China

Geoporphyrins, isolated from source rock, were analyzed on electron ionization mass spectrometry （EIMS） and Tandem mass spectrometry （MS/MS）. The spectrum of ElMS shows that the geoporphyrins are mainly composed of two types: DPEP and eito. Most of the porphyrin carbon numbers are greater than C32. The daughter spectra of the molecular ions (C34-36DPEPs) display the loss of methyl and ethyl groups, which indicate there are ethyl and propyl groups in the mother ions. The average condensed structural formulae, derived from the data of the spectra on MS/MS, have clearly shown the composition of the substituents on the porphyrin pyrrole ring, and the regular changes of the substituents reveal the characteristics of the dealkylation of the porphyrins in the geosphere.

关键词： Tandem mass spectrometry geoporphyrins condensed structural formula dealkylation.