Reservoir Evaluation Of Xu'er Gas Reservoir In Hechuan-Anyue Gas Field

Hechuan-Anyue gas field locates in transitional district of central and southern of Central Sichuan, which has made great progress with prospecting for a few decades. The mian characteristics of Hechuan-Anyue gas field are of gentle structure, tight reservoir, complex pore structure, strong heterogeneity and low productivity of a single well. It is hard to develop owing to complex gas-water relationship and gas production with water. By using the data of geology, logging and production test, this paper studies the research region's reservoir of Xu'er gas field with theories and techniques of sedimentary, geology of logging, reservoir geology, sequence stratigraphy etc. , The main poinis are as follows:(1) Basing on the predecessors'thin-layer division and combining the contrast analysis of well logging data, the Hechuan 1 well is chosen as standard well and the connecting-well section which can cover the whole region is constructed. Then, regarding the lithology curve as a major contrast and dividing foundation, meanwhile referencing to the electric property curve, finally the subdivision contrasts of 62 wells within the region are completed.(2) The analysis of core facies-log facies and combining the detailed description of cores and indoor observations and studies of large numbers of core slices indicates that the research region's reservoir in member 2 of Xujiahe are mainly developed from the underwater distributary channel and mouth bar sandbodies of the fan-deltaic front, and the research region sedimentary facies model is also constructed.(3) The rock types in the reservoir are mainly debris-feldspar and feldspar-debris sandstone. Mercury-injection tests have shown that the pore structure of the reservoir is mainly small pore and micro throat, the main pore types are as follows: primary intergranular pore, intergranular dissolution, intragranular corrosion pore and mould pore and that the reservoir have low porosity, low permeability and ultra-low porosity, ultra-low permeability and poor physical properties.(4) Secondary interpretation to log information has been done with the BP neural network based on the standard processing of logging data. This paper establish regional reservoir evaluation standard based on the analysis of porosities for core samples, mercury injection tests, capillary pressure and pressured-mercury testing and research the reservoir heterogeneity. Combined with practical conditions of production, it is generally accepted that sandstone section with porosity≥6% is reservoir, and which with porosity≥6% and water saturation≤55% are effective reservoir. Heterogeneity is also comprehensively studied. The results show that the reservoir is mainlyâ…¢andâ…¡type in T₃x2¹ and T₃x²2, but theâ… type is relatively developed in T3x22.(5) Finally, based on the establishment of characteristic of reservoir reservoir and the predominant factors what control the reservoir development, this paper have done some estimation and prognosticated the excellent gas prone area of the horizon-tal reservoir for the secondary exploration in member 2 of Xujiahe formation in Hechuan-Anyue gas field.