Study On Tight Gas Reservoir Horizontal Wells Geological Conditions Of He8 Formation At Eastern Part Of Sulige Gas Field

Tight sandstone reservoirs of He8 Formation have the characteristics of dense lithology and complex geological features at eastern part of Sulige gas field. Horizontal well is increasingly applicated with the research become more and more mature on the geological characteristics in Sulige gas field. However, the horizontal wells are completely different in productivity which affected by the complex geological factors. The horizontal well’s development which influenced by the investment is still at the experimental stage at eastern part of Sulige gas field. In order to figure out the factors which affecting the differences of productivity, the author prove the suitable economic and geological conditions for horizontal well development combine with the microscopic geological experiments of reservoir, according to the contradiction of large-scale application of horizontal well in study area during development, Finally, the favorable zone for horizontal well development has being confirmed.The following conclusion has been obtained which based on the characteristics of basic and microscopic geological features:Based on the actual situation of development of He8 formation, the author gets four parameters according to the economic evaluation research with the financial net present value method which can provide basis to further geological parameters’ calibration for the development of horizontal well:the accumulative gas production of single well>2493×104m3, controlled geologic reserves>0.5×108m3, reserve abundance> 0.45×108m3/km3, daily gas production of the single well> 0.76x 104m3/d.This study calculates the parameters of geological (reservoir thickness, permeability, porosity, gas saturation, electric property) and microscopic experiment under the given conditions (gas price is ￥1.1 yuan/m3) for horizontal wells in the study area:when the low limit of reservoir thickness value is 4m, permeability >0.28×10-3μm2, porosity> 8.85%, gas saturation> 53.4%; According to the above study, the author demarcates the low limit of electric property using logging principle, the Archie formula and the cross-plot method: acoustic transit time △t>230μs, resistivity>30Ω·m, density<2.55g/cm3, shale content<14%.According to the criteria of economic and geological evaluation and the correlation between permeability and characteristic parameter of micro experimental, this paper calibrates the critical value which suitable for horizontal well development of displacement pressure(< 0.98MPa), pore radius median(> 0.9μm), saturation of irreducible water(< 50.4%) and the range of gas-water seepage phase(43.0%) from the experiment of high pressure mercury injection and relative permeability curve when the permeability valued as 0.28×10-3μm2. The type I and type II curve come from the experiment of high pressure mercury injection and relative permeability curve are appropriate for development of horizontal well.Finally, the favorable area has been divided by combinate the threshold value of sand body, porosity, permeability and gas saturation in He8 formation at eastern part of Sulige gas field. And the proportion of favorable area are 413.11km2 and 589.86km2 in He8-1 and He8-2, respectively.The results show above combine two aspects which include the economic and geological factors can guide the practical operation.it is benefit for the development of efficient and reasonable of horizontal well in study area.