Comprehensive Geological Evaluation Of Gudian Rift In South Of Songliao Basin

Gudian rift lies in the South of central depression of Songliao basin. It is a typical dustpan fault depression which downfault east and overlap west. Well Lingshen1 accessed to high gas breakthrough revealed that the deep of Gudian rift has big exploration potential, but so far the rift is of very low exploration degree with only two prospect wells drilled to deep formations. To clear the deep rift geological characteristics and many other issues we developed this comprehensive geological evaluation to obtain further recognition of this fault depression and provide reference for further exploration.This comprehensive research focus on well Lingshen1 which is the only prospect well in Gudian fault depression. Using the drilling data of Lingshen1 well and the seismic data, combing the analysis of paleontology and regional formations, we divided strata and completed the deep structural interpretation. Based on the research above , we identify the structure of deep Gudian fault depression. Gudian rift has two north-south secondary hydrocarbon generative depressions, between which exists a uplift. Gudian rift has gone through the rift, depression and post-reversal evolution. Gudian fault has controlled the deposition of Gudian rift especially during the deposition of Shahezi formation. It developed four formations in the deep of Gudian rift, up toward, they are upper Jurassic Huoshiling formation, Lower Cretaceous Shahezi, Yingcheng and Denglouku formations. Yingcheng formation has the most dark mudstone, and Shahezi formation comes second. The dark mudstone of top Denglouku formation has good organic matter type ofⅡ₁-Ⅰ, and the dark mudstone of lower Denglouku formation to Huoshiling formation is ofⅡ₂-Ⅲtype. The main source rock of deep formations is the gas source rock of lower Shahezi group and Huoshiling group. Organic matter threshold is about at 1170m, and it went into mature-high mature stage from Yingcheng time. The main rock types in deep reservoir are sandstone and conglomerate , which develop intergranular , intragranular dissolution porosities and structure dissolution joints. It is special low porosity and low permeability reservoir because the effective porosity and permeability are very low, and the physical property of Shahezi formation is relatively good. Diagenesis is divided into two phases. Compaction dominated the diagenesis action , and other diagenesis actions such as metasomatosis and dissolution also exist. Well Lingshen1 gas pool is a lithology-struction gas trap as well as self-generation and self-bearing. Faults and unconformities are the main channels of deep gas migration in Gudian rift. There are several accumulation models in the deep of Gudian rift. The successive gas breakthroughs show that glutenite of deep formations is becoming a hot pot for present exploration. The result of basin simulation research indicates that Gudian rift has large resources potential, and the glutenite reservoir is the important exploration target. Besides, this research built up the seismic recognition mode for glutenite, and proposed beneficial exploration belt and one favorable target based on the inversion forecast result of glutenite facies.