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China United Coalbed Methane Corp. is state-owned company in China, which has exclusive rights to explore, develop and produce coalbed methane in cooperation with overseas companies. The company was established in 1996. Wikipedia.

Yu H.,Sinopec | Ren S.,China University of Petroleum - East China | Zuo J.,China United Coalbed Methane Company
Shiyou Xuebao/Acta Petrolei Sinica | Year: 2012

To describe movement laws and complex flooding mechanisms of air and foam during the air-foam flooding, we built a mathematical model for the air-foam flooding based on an assumption of the correlation between phases and components. This model used the mathematical model of in-situ combustion as reference and combined the processing of physicochemical parameters with an air low-temperature oxidation dynamics equation and an empirical model of the foam flooding. The present paper examined the closure of this model and proposed a solution way to corresponding numerical models. A concept model was built and the oxidation dynamics model was modified through an experimental match with the air-foam flooding, and consequently the sensitivity towards influential factors for the displacement mechanism of the low-temperature oxidation flooding was assessed in an air-foam flooding simulation. The result shows that the displacement effect is matched considerably well with the water breakthrough time during the whole experiment. The air-foam flooding characteristic of a better effect and lower cost is fit for heterogeneous reservoirs with variation coefficients between 0.7~0.8 or for positive-rhythm reservoirs in the late water flooding stage. Many methods can be beneficial to increasing the air-foam flooding effect, such as high temperature and pressure, water injection at higher position while production at lower position, switchover to the foam flooding as the moisture content reaching to 96% by the water flooding and an inverted seven-spot well pattern in the water flooding. Besides, a better flooding effect can be also achieved as the gas liquid ratio keeps between 1:1~2:1, the air injection rate ranges in 0.1~0.2 PV/a or the air-foam alternating-air injection pattern is applied.

Liu X.,China University of Petroleum - East China | Qi Y.,China University of Petroleum - East China | Hu A.,China United Coalbed Methane Company | Zhao P.,Petrochina | Liu C.,China University of Petroleum - East China
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2011

Inflow performance relationship(IPR) in single-phase(water) coalbed methane wells provides the basis for the reasonable operating practice and dynamic analysis. The mathematical models of IPRs for Darcy and non-Darcy flow in coalbed methane(CBM) wells are developed based on the fluid mechanism in porous medium. The IPR curves are obtained with the field examples in Ordos Basin. The results show that the small errors of less than 12% between the prediction and measured values are achieved due to the reservoir parameters, fluid physical property and non-Darcy skin factor. The IPR should be analyzed by the Darcy model with constant supply boundary pressures for the low flow velocity. However, the non-Darcy model should be involved while the Reynolds number is over 0.3 and water production is more than 30 m3/d. During the initial pumping production, the water flow rate and coal particle migration can be controlled due to the increase of pressure drop, which is beneficial to water flow. And an increased pressure drop from 0.44 MPa up to 3.68 MPa leads to the enhanced water production from 10 m3/d to 40 m3/d. The increase in the integrated flow conductivity of coalbed and deliverability occurs with the increment of permeability. And the increase of permeability from 0.9×10-3 m2 up to 6.15×10-3 m2 leads to an increment in water production from 3.5 m3/d to 15.9 m3/d. The decrease of skin factor makes the IPR curves move towards the right direction. And the reduction in skin factor from -3.10 to -4.85 yields the increase of water production from 34.8 m3/d up to 45.6 m3/d.

Ren J.,China University of Petroleum - East China | Zhang L.,China University of Petroleum - East China | Ezekiel J.,China University of Petroleum - East China | Ren S.,China University of Petroleum - East China | Meng S.,China United Coalbed Methane Company
Journal of Natural Gas Science and Engineering | Year: 2014

Abundant tight sands rich in natural gas, as a kind of unconventional energy source, have been discovered in the Ordos Basin, Central-North China, which can contribute greatly to the sustainable supply of natural gas in China. In this paper, the geological and petrophysical characteristics of a typical tight sand gas reservoir in the Upper Paleozoic of the Ordos Basin were investigated and correlated to the productivity of gas wells. Several important petrophysical relationships were revealed based on data from drill cuttings, core, and well logging, including porosity versus permeability, stress sensitivity to permeability, and rock density versus porosity. Their effects on well's productivity were discussed. The productivity of the targeted reservoir was analyzed and classified using a formation capacity method (K·. H factor), and was compared with the production data of similar tight sand and low permeability blocks in the region, which can provide good reference for the field development. © 2014 Journal of Pediatric Urology Company.

Li D.Q.,China University of Petroleum - Beijing | Li D.Q.,China United Coalbed Methane Company | Zhang S.C.,China University of Petroleum - Beijing | Zhang S.A.,China University of Petroleum - Beijing
Journal of Natural Gas Science and Engineering | Year: 2014

Taking the technology of horizontal well fracturing through interlayer to coal seam as the simulation object, the true triaxial test system was employed for the first time in a fracturing stimulation experiment of layered combination specimens comprised of natural rock. The effects of in-situ stress, natural fracture and elastic modulus on hydraulic fracture propagation were studied. On this basis, the effects of different geological and engineering factors on fracture propagation in coal seams were studied quantitatively using the three-dimensional hydraulic fracturing numerical simulation model based on the fluid-solid coupling finite element method. The results indicate that the roof and floor in coal-bearing stratum with larger differences (5MPa) between vertical stress and the maximum horizontal stress is preferential in the implementation of horizontal fracturing through interlayer to coal seam. The influence of a natural fracture on the propagation of a hydraulic fracture is mainly related to the width of the natural fracture, the injection pressure in the hydraulic fracture and the angle of approach. Under high injection pressure, the impact of natural fractures on hydraulic fracture propagation was significantly lessened. Depending on the developmental degree of a natural fracture, the effect of the approaching angle between the natural fracture and the hydraulic fracture will be smaller. The lower stress difference, elastic modulus difference and permeability difference between layers and higher pumping rates are beneficial in forming longer fractures in a coal seam. Permeability anisotropy characteristics of a coal seam and its roof and floor make the fracture geometry higher, wider and shorter. The experimental and numerical simulation study achievements provide a theoretical basis for effective implementation of this new technology in coalbed methane development. © 2014 Elsevier B.V.

Duan P.-J.,China University of Petroleum - Beijing | Wang Z.-Y.,China University of Petroleum - Beijing | Zhai Y.-Y.,China United Coalbed Methane Company | Zhang D.-L.,Petrochina
Meitan Xuebao/Journal of the China Coal Society | Year: 2011

Taking advantage of the rock mechanical analysis approach, the theoretical research and discussion referring to the depressurization rate under the different stress state of coal rock around a borehole in the initial stage of exploitation was carried out, and the mechanical analysis model about the control to the depressurization rate was built, and the upper limit values of the reasonable depressurization rate in the process of exploitation were determined with considering the practical engineering test data in Hancheng. Meanwhile, the variation of the upper limit values against the depth of the reservoirs was given according to the research to several wells data. The results show that the upper limit values are linear increasing with the depth of the reservoirs, and mechanical characters of coal rock have a greater effect on the reasonable depressurization rate. Thus, it can be achieved to make the permeability rise or maintain at a high level by controlling the change of the depressurization rate of the bottom hole pressure.

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