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- Title
基于改进的岩石物理模型表征页岩天然裂缝特征.
- Authors
管全中; 董大忠; 张华玲; 张素荣; 吕修祥; 王玉满
- Abstract
In order to provide technical support for the shale gas exploration and development in the Lower Silurian Longmaxi Formation of the Sichuan Basin, this paper takes the Longmaxi Formation in the Changning and Fuling shale gas fields as the research object to quantitatively characterize the development characteristics of natural fractures in Longmaxi Formation shale by means of helium pycnometry, X-ray diffraction (XRD), true density testing and other methods, with the aid of the modified petrophysical model. Then, the development types and genetic mechanisms of natural fractures and their influences on shale gas development are discussed. And the following research results were obtained. First, the modified petrophysical model can accurately describe the pore system in the Changning shale with a fitting rate of 0.74. Second, the development of natural fractures in the shale is different in different regions. The natural fractures in the Changning Shale Gas Field, controlled by basement thrust faults, decollement layers and internal folds, are locally developed and filled with calcareous, and the average fracture porosity is 0.15%. In the Fuling Shale Gas Field, however, natural fractures, mainly controlled by reverse faults and slippage effect, are commonly more developed and unfilled or semi-filled with siliceous, and the average fracture porosity is 1.30%. Third, under the formation conditions, the opening of natural fractures is different. The natural fractures in the Changning Shale Gas Field are basically closed with a weak flowing ability while those in the Fuling Shale Gas Field are relatively open with a strong flowing ability. Fourth, the occurrence mode of shale gas is influenced by natural fractures and it is internally dominated by free gas. The initial gas production of shale gas well is higher. In conclusion, the regression coefficient is introduced to calculate the actual total organic matter content, which promotes the modified petrophysical model to describe matrix pores and fracture pores more accurately. What's more, the development of natural fractures in the shale pay zone of the Sichuan Basin is relatively beneficial to shale gas enrichment and exploitation, but its effect will be weakened under the formation conditions.
- Subjects
SICHUAN Sheng (China); SHALE gas; GAS fields; NATURAL gas prospecting; GAS wells; COMPOUND fractures; SHALE
- Publication
Natural Gas Industry, 2021, Vol 41, Issue 2, p56
- ISSN
1000-0976
- Publication type
Article
- DOI
10.3787/j.issn.1000-0976.2021.02.007