东海西湖凹陷区深层压力突变成因及预测方法

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中图分类号：TE142；TP319 文献标志码：A

Abstract： The abrupt change of deep formation pressure is a prominent problem in Xihu Depressionof East China Sea Basin， which makes itdificult topredictduetoitsunknowncauses，andcanseriouslyrestricts thesafeandeficient drllingoperation.In order to explain this special phenomenonofthe pressureabrupt changein thetarget block，acomprehensive Bowers method （loading-unloading curve method）andanacoustic velocitydensitycrosslot methodwereused to identifythe pressureforming mechanismsofdiferentlayers indeepformationandtheinfluenceof lithologyonpressureabruptchange.Further，anew pore pressure prediction modelfordeep formation was establishedbasedoncorrction parameters that exclude the influenceof highabundanceorganic materandnano-scaleorganicpores，butconsideringthe influenceof multiplesources such as pressure forming mechanism，lithologychange，rock mechanical properties，rockconduction propertiesandrock volume properties.Theresultsshowthatthe pressre abruptchange is mainlycausedbythe pressure forming mechanismand lithologyof different deep strata in XihuDepression.The pressure surge inthemiddle Pinghu Formation is mainlycaused by hydrocarbon generationand pressre transferof non-source rocks，andthepressurereversal inthelower PinghuFormationis mainlycaused by structural compresion of non-source rocks.Combined withthe measured data offour wels in the study area，it is verified that the prediction error of the new model is controlled within 5.0% ，and the average error is only 2.3% ， which shows good applicability and high prediction accuracy of the new model.

Keywords： Xihu Depresion;； pressure abrupt change； pressure formation mechanism； multiple sources； measured data

东海盆地西湖凹陷是中国近海海域最大的新生代沉积盆地[1]，根据大量钻井实测资料表明，西湖凹陷深部地层中不同层段、不同岩性的孔隙压力分布规律复杂多变，尤其平湖组压力突变的特殊压力现象导致出现先增压后降压系统特征。（剩余12331字）