The Research On Well Logging Interpretation Methods For The Shanxi Formation And He₈ Member In Upper Paleozoic Of Yan'an Area In The Ordos Basin

Yan'an gasfield in the Ordos basin is another major breakthrough in the field of natural gas exploration in recent years. In order to further clarify gas reservoir characteristics of the region and response characteristics of log data of the gas reservoir, to assist the comprehensive exploration and development of the region in the next step, it is particularly important and extremely urgent to carry out research of logging data and log interpretation methods in the region.According to the theory of sedimentary rock and by means of previous data and field awareness, based on outcrop,cores and well logs, The author of this article redefined the stratigraphic sequence of the study area and summed up type of sedimentary facies and microfacies of Shanxi formation and He₈ member reservoirs, which laid the foundation for an accurate understanding and research about the reservoir. Study shows that Shanxi formation is mainly meandering river delta facies and He₈ member is braided river delta facies.Under the guidance of Identified macro sedimentary facies, the author detailly studied the characteristics of Shanxi formation and He₈ member reservoirs by using of core analysis, cast information sheets as well as information on mercury. The author analysed the pore structure of reservoirs by using of experimental analysis of mercury which was commonly used. It is worth mentioning that the author used of new technology of nuclear magnetic resonance logging to analysis the pore structure of reservoirs.On the basis of a clear understanding of reservoir characteristics , the author systematically studied lithology, physical properties, logging response features and gas-bearing characteristics of Shanxi formation and He8 member reservoirs, and developed a new ways to identify of lithology by use of the electrical characteristics of the logging. In addition, the author Proposed a new method of lithology identification by use of photoelectric and natural gamma curve.In order to obtain accurate reservoir parameters, the author built log interpretation models in different reservoir and lithology by using of sophisticated way. At the same time , the author regressed Porosity,Penetration and Water saturation formula in a different block by using a of core analysis data. In addition, all the calculation formulas were verified. The results show that the calculation formulas were reliable and could meet the needs of log interpretation. Secondly,the related data were standardized to achieve accurate reservoir parameters.These data incloud logging data,core analysis and information sheets.Here crossplot is proposed to determine gas/water distribution so that can identify accurately gas,gas-water,bad gas and dry layer in Shanxi formation and He₈ member reservoirs of Yan'an gasfield are determined by threshold value method which conclusions are verified during the following several wells log interpretation.In a word,adaptable logging interpretation model and corresponding equation were established for this field. All the above mentioned the logging parameters formula and models were verified to be reliable and practical by the core analysis and well test results which could truly reflect the characteristics of the reservoir.