Formation Conditions of High-CO2-Content Hydrocarbon Pool and Its Implication for CO2 Geological Storage

Abstract

As the increasing obvious trend of “global warming”, reducing emission of greenhouse gas, especially CO₂ has attracted extensive attentions. The previous research has proved that the method of geological storage is an effective way to reduce CO₂ emission. And depletion hydrocarbon pools, which possessed favorable sealability and facilitated with the wells of production and injections, formed an ideal storage place for CO₂. However, due to its relative higher activity compared to the oil or gas, not all depletion hydrocarbon pools can be effective for CO₂ storage. Thus, the hydrocarbon pool formed in which conditions that is also effective to seal CO₂ becomes the important problem that needs to be resolved. The discovery of the high-CO₂-content hydrocarbon pool provide a favorable condition to solving this problem, and clarifying the forming conditions of this kind of hydrocarbon pool serves to deepen the understanding of the necessary conditions of CO₂ geological storage. In this article, the high-CO₂-content QHD29-2 oil-gas pool located in Bohai Sea, Eastern of China is taken as an example, and its formation condition is studied. According to this study, the range of CO₂ content in QHD29-2 oil-gas pool is 46.26%~59.39%, and the stable carbon isotopic (δ13C) content is −6.4‰~−5.2‰, while helium isotope(3He/4He) content is (5.49~6.21)Ra (Ra = 3He/4He = 1.400E–6), the abiogenetic gas is generated from mantel sourced volcano, and carried by the active part(growth index>1.04) of the deep and major fault that adjacent to hydrocarbon traps. Integrated analysis of 3D seismic data, well logging data, formation water and gas chromatography-mass spectrometry analysis of oil is conducted, it is concluded that QHD29-2 oil-gas pool is possibly sits in a fluid compartment, which consist of fault, recesses and abnormal high pressured mud strata both at the top and bottom, and the well spatial sealability of this fluid compartment caused locally enrichment of CO₂. Thus, the study of the deep buried fluid compartment related hydrocarbon pool in the sedimentary basin is significant for CO₂ geological storage research.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015