Origin of the Overpressure and Hydrocarbon Accumulation Characteristics of Bedrock Buried Hills in the Deepwater Area,Qiongdongnan Basin
Hu Lin
Hu Qianwei
Wang Siyu
Jiang Rufeng
Wang Ziling
Zhao Chen
Tian Lanxi
Zhang Chaomeng
Bian Kaige
Abstract：Deepwater reservoirs are the hotspot of global oil and gas exploration.With the continuous development of deepwater exploration,overpressure bedrock buried hills have gradually become an important successor field.The breakthrough of Lingshui 32-1 buried hill gas reservoir in the western deepwater area of the Qiongdongnan Basin reveals the insider fracture reservoir as well as the formation of large gas fields,and demonstrates the exploration potential of Lingnan Low Uplift buried-hills.However,overpressures are prevalent in buried hills,and how overpressure affects gas reservoir accumulation is a vital issue that needs to be solved urgently.To explore the overpressure characteristics,development mechanism of overpressure,and the relationship between overpressure and hydrocarbon accumulation,the drilled cores,thin-section observation,numerical simulation,and fluid inclusions analyses were utilized,revealed the two pressure systems,with an upper pressure coefficient of 1.68 and a lower pressure coefficient of 1.76 to 1.85,and two phases of gas filling from 3.0 to 1.9 Ma and from 1.8 Ma to the present day,respectively,and the gas filling process is consistent with the overpressure formation.Lingshui 32-1 buried hill consists of gravelly reservoirs,weathered crust reservoirs,tight interval,and internal fracture reservoirs.The fracture,basement fault,and vertical microfracture are the main channels for natural gas migration.The overpressure mechanism of Lingshui 32-1 buried hill is mainly due to disequilibrium compaction and hydrocarbon pressurization in the early stage,and lately controlled by lateral transmission of fluids pressure.The timing of strong overpressure formation matches well with the gas filling.The overpressure within the depression and the gas filling process into the buried hills control the gas reservoir accumulation.Eventually,an accumulation model of overpressure-controlled hydrocarbon generation,transmission,filling,and preservation developed.This study provides an important basis for further exploration of bedrock buried hill reservoirs in the deepwater area of the Qiongdongnan Basin.
Keywords：overpressurebedrock buried-hillsgas fillingdeepwaterQiongdongnan Basinpetroleum geology
Publication Date：2025-02-14
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：20( 433-452 )