沾化凹陷沙四段上亚段滩坝沉积特征及其主控因素

Sedimentary characteristics and main controlling factors of the upper fourth member of Shahejie Formation in Zhanhua depression

在岩心观察和分析测试的基础上,结合录井、测井等资料,运用沉积学理论,对沾化凹陷沙四段上亚段滩坝的沉积特征和分布规律进行研究,并分析其主控因素。结果表明,研究区发育砂岩滩坝和碳酸盐岩滩坝2种类型;其中砂岩滩坝主要分布于罗家鼻状构造及其周缘,岩性以灰色粉、细砂岩为主,分选好、成熟度高;碳酸盐岩滩坝分为生物礁和灰岩滩坝2种类型,生物礁主要沿义东断裂带呈长条状分布,岩性以灰色灰岩和灰质白云岩为主,分选较差,一般为原地沉积或仅经过短距离的运移;灰岩滩坝主要分布于邵家洼陷,岩性以灰色灰岩为主。古气候、古地貌和古物源为沾化凹陷滩坝沉积的主控因素,独特的古气候条件决定了研究区水量相对缺乏,与南缓北陡的古地貌特征和西部物源缺乏的古物源特征共同控制着滩坝沉积的区域、规模和类型。

Based on core observation and test and mud logging data analysis,the sedimentary characteristics and distribution of beach-bar in the upper fourth member of Shahejie Formation in Zhanhua depression were researched,and the main controlling factors were analyzed. The results show that there are sandy beach-bar and carbonate beach-bar in the study area. The sandy beach-bars mainly distribute in Luojia nose structure and in neighboring regions. The lithology of the sandy beach-bars is mainly gray fine sandstone and siltstone with good sorting and high maturity. Carbonate beach-bar is classified into organic reefs and limestone. The organic reefs mainly distribute along Yidong fault zone with a strip shape,and the lithology is mainly gray limestone and limy dolomite with poor sorting. They deposited generally in situ or settled down after a short distance migration. The limestone beach-bars mainly distribute in Shaojia sag,and the lithology is mainly gray limestone. The main controlling factors are paleo-climate,paleo-landform and paleo-provenance:the specific paleo-climate resulted in a lack of water in the study area;the ancient landform developed a steep slope zone in the north and a gentle slope zone in the south;and the paleo-provenance was characteristic of lacking western provenance. The distribution area,scale and type of the beach-bars are controlled by the three factors jointly.