High Efficiency Drilling Control Technology for Shale Oil in Jiyang Depression

According to the geological characteristics of shale oil in Jiyang depression, the formation mechanics test was carried out to study the influence of well deviation orientation on wellbore stability, thus the high-efficiency drilling control method was put forward. The above research results were applied in the test wells, and the purpose of high-efficiency drilling was realized.

Evaluation Method of Movable Shale Oil Resource: A Case Study of the Shahejie Formation in the Dongying Sag, Jiyang Depression

Although China has enormous shale oil resource potential, oil recovery is limited at present, largely because its movable resource is not evaluated. In this study, an evaluation method for movable shale oil resources is proposed. The process first evaluates the total shale oil resource (Qtotal), and then two-dimensional nuclear magnetic resonance (NMR) technology is used to measure the free oil ratio (Rfree) and further define the quantitative relationship (F) between the movable ratio (Rm) in the free oil and centrifugal force. The movable oil resource is calculated by the total shale oil resource, free oil ratio, and movable oil ratio (Qm = Qtotal × Rfree × Rm). This method was applied to the Shahejie Formation of the Dongying Sag, Jiyang Depression, in Bohai Bay Basin, and the relationship between the free oil ratio (Rfree) and depth was established based on several core 2D NMR data. Based on the formation pressure, flowing bottom hole pressure, and relationship (F), the movable shale oil ratio (Rm) in the target area was determined. The results showed that the movable shale oil ratio (Rm) of the lower Es3 is approximately 18.9–20% in the depth range of 3,200–3,700 m, and the movable shale oil resource is approximately 2.52 × 108 t.

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

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.