Log Evaluation Technology Research On The Geology Survey Of Shale Gas In Chongqing Northeast CK Area

At present domestic shale gas is still in the early exploration stage, and shale gas evaluation criteria are quite different in different areas. The accumulation characteristics of shale gas reservoir are different from conventional reservoirs, causing the geophysical characteristics different, which increases the difficulty of applying logging technique to identify the shale gas reservoirs. In addition, since it is costly and time-consuming for the imaging logging and coring methods concentrating on the various complex lithology identification, it is difficult to realize their widespread applicaiton in every geological survey wells. Therefore, it is essential to to improve the accuracy of identifying and evaluating of shale gas reservoirs in conventional well logging.Based on the mineral composition, reservoir physical properties, geochemical parameters and gas content, etc., the logging evaluation method was established for downhole Cambrian shuijingtuo formation shale gas formation in CD4 Well in northeastern chongqing.(1)Shale content model is established based on the CNL and AC, while sandy content and limestone content model is established based on the three porosity curves.(2)The effective porosity is determined by the neutron- density intersection method. In addition, permeability is calculated using the Timur theoretical formula.(3)TOC model is established based on the DEN and AC.(4)By means of Langmuir equation, the adsorbed gas and free gas content is calculated with regard to the temperature, pressure and TOC, calculation of adsorbed gas and free gas content.We has carried out extensive research, and corresponding results are as follows:.1.Summarizes the logging response characteristics of the downhole Cambrian shuijingtuo formation shale gas formation in the well.(1)Natural gamma ray response characteristic value is higher, especially abnormally high in the fault fracture zone the value.(2)Acoustic time is relatively high, with frequency hopping phenomenon as the crack is developing.(3)Compensated neutron values are high.(4)Lateral resistivity displayed as high value. high lateral resistivity is always caused by high gas saturation, while water filling cracks development makes lateral resistivity slightly low.(5)Due to the low density value of kerogen, shale gas reservoir compensation density value is low.2.The lithology identification chart is established. it is effective to identify the lithology of the mud shale, limestone and dolomite with different particle diameter according to the chart,.3.Mineral component model and TOC model of high degree of relevance is established,which is high correlated and fitted compared to the experimental analysis of core data.4.According to the improved Langmuir equation and such parameters as gas saturation, effective porosity, temperature and pressure in the formation, the model of adsorbed gas and free gas is established.The adsorbed gas dominates in CD4 Well and the total gas content shows positive correlation with depth.5.Shale gas fluid recognition template is established. Based on TOC, the template can be utilized to effectively identify and evaluate the reservoir quality of shale gas in CD4 Well according to the different shale gas reservoir physical parameters...