Prestack Seismic Prediction Of Tight Sandstone Available Reservoirs In Third Member Of Shahejie Formation In Areas Adjacent To Qingshui Sag In Western Depression Of Liaohe

Qingshui Sag is the largest hydrocarbon-generating sag in Liaohe Depression. Meanwhile, while the third member of Paleogene Shahejie Formation was deposited large areas of clastic reservoirs were continuously distributed, dominated by low porosity and low permeability, having a direct contact with source rocks, forming good geologic conditions for the formation of tight sandstone gas reservoirs. For a long time, because of the strong reservoir heterogeneity and the difficulty in predicting available reservoirs, the further exploration of tight sandstone hydrocarbon accumulations in the study area has been restricted. In the paper, aimed at the difficulty, based on the sensitive elastic parameter optimizing of petrophysical analysis, the technique of prestack simultaneous inversion has been applied to predict the distribution characteristic of sand bodies; oil testing method has been integrated to determine boundaries of available reservoirs and reservoir type, and the technique of prestack seismic inversion has been made use of to further predict the spatial distribution properties of available reservoirs.1. Through large quantities of method tests, it has been determined that Xu-White petrophysical model is the relative suitable method for the tight sandstone secondary wave prediction in the study area. Judging from the results of sensitive parameter analysis, the lithology and properties of tight sandstone reservoirs can be predicted, but hydrocarbon-bearing prediction cannot be done;2. By analyzing well logging data, oil testing data, core data and the like, the lower boundary of available reservoirs has been determined in the third member of Shahejie Formation. It has been thought that mud content is closely related to permeability as a key factor in determining availability of the reservoirs;3. The prediction results have shown that tight sandstone available reservoirs were relatively developed in the upper and middle parts of the third member of Shahejie Formation in Qingshui Depression, with the latter in northern Qingshui Depression as the most favorable area for tight sandstone hydrocarbon pools, while they were hardly developed in the lower part.