鄂尔多斯盆地南部三叠系延长组泥岩压实系数与古压力特征

(1.中国地质调查局,北京,100037; 2.陕西延长石油(集团)有限责任公司 研究院,陕西,西安 710065; 3.中国科学院 地质与地球物理研究所,北京 100722)

鄂尔多斯盆地南部; 泥岩压实系数; 古压力; 三叠系

Compaction coefficient and paleo-pressure characteristics of Yanchang Formation of Triassic in southern Ordos Basin
YANG Chao1,HE Yong-hong2,LEI Yu-hong3,SI Peng1

(1.China Geological Survey,Beijing 100037,China; 2.Research Institute,Shaanxi Yanchang Petroleum(Group)Co.,Ltd.,Xi'an 710065,China; 3.Institute of Geology and Geophysics,Chinese Academy of Science,Beijing 100726,China)

southern Ordos Basin; mudstone compaction coefficient; paleopressure pressure; Triassic

备注

利用钻井、录井、测井等数据资料,对鄂尔多斯盆地南部三叠系延长组泥岩压实系数和古压力进行深入研究和剖析。研究表明,泥岩的压实系数明显受到泥质含量及矿物组成的影响,泥质含量和压实系数具有正相关性。富县地区泥岩压实系数最大,其次为旬邑地区,黄陵地区压实系数较小。通过对有机质导致的声波差异进行校正,恢复研究区最大埋深古压力,富县地区过剩压力最大,介于8~10 MPa; 旬邑地区,最大埋深时期泥岩剩余压力为6~8 MPa; 而黄陵地区,由于泥岩厚度较薄,沉积速率相对缓慢,异常压力也较低,介于4~5 MPa.

Based on the the data of drilling and logging,a detailed examination was made on the mudstone compaction coefficient and paleopressure of the Triassic in the southern Ordos Basin.The results show that the compaction coefficient of mudstone is obviously influenced by the content of clay and mineral composition.The higher the sediment shale content,the finer the grain size,the greater the original porosity; the greater the slope of the compaction curve,the faster the pore loss of fine grain sediment,compared with the coarse grained mudstone in the conditions of effective stress.The compaction coefficient of mudstone in Fuxian area is the largest,followed by the Xunyi area,and the coefficient of compaction is smaller in Huangling area.The mudstone in Fuxian area is thick and the deposition rate is fast,which makes it more favorable to the formation of undercompaction.Therefore,the excess pressure is the largest,in the range of 8~10 MPa.And the residual pressure of mudstone is 6~8 MPa.In Huangling area,the deposition rate is relatively slow and the abnormal pressure is low,which is 4~5 MPa.