Coupling between tectonic activity and diagenetic evolution of a clastic buried hill—a case study from Gubei low buried hill in Jiyang Depression of Bohai Bay Basin

Abstract

This paper aims to gain new insights into clastic buried hill reservoirs. For this purpose, the Permian sandstone reservoirs in the Upper Shihezi Formation, Gubei low buried hill, Jiyang Depression, was taken as the object. Referring to the evolution histories of reservoirs and tectonics, the diagenesis of the reservoirs and its coupling with tectonic activity were investigated, with the aid of techniques like core observation, casting sheet observation, scanning electron microscopy (SEM), cathode luminescence, electron probe, back scattering, fluid inclusion, and pore permeability tests. The results show that the Permian sandstone reservoirs in the Upper Shihezi Formation, Gubei low buried hill, Jiyang Depression, are low-porosity, low-permeability reservoirs with complex diagenesis. The diagenetic evolution sequence can be summarized as early feldspar corrosion/kaolinite cemention/early pyrite cemention→carbonate cemention/secondary enlargement of quartz→quartz corrosion/corrosion of quartz and its secondary enlargement→late calcite cemention→late pyrite cemention/carbonate corrosion/late feldspar corrosion/corrosion of dissolvable miscellaneous matrix; compaction effect exists throughout the evolution process. The reservoirs went through (I) shallow burial epidiagenesis, (II) near-surface hydrothermal diagenesis, (III) deep burial alkaline diagenesis, and (IV) continuous burial acid diagenesis. The diagenetic evolution of these four stages is significantly affected by tectonic activities, and the article lists the evidence that diagenesis is affected by tectonic activity. The research results lay the basis for the prediction and evaluation of the Permian sandstone reservoirs in the Upper Shihezi Formation, Gubei low buried hill, Jiyang Depression, and shed new light on the exploration of tight sandstone reservoirs.