Research For The Development Technique Of Low Permeability Gas Reservoirs In Sichuan Basin

With a gradually increasing of demand of natural gas in the world, the production and reserve-production ratio of conventional gas reservoir appearing a gradual decline, unconventional gas resource is considered as the most hopeful resource supplement. Thus accelerating the exploration and development of low permeability gas reservoir becomes an inevitable trend of the energy industrial development in the century.Sichuan has become one of the most important industrial gas bases in China through over forties years of exploration and development. With the unceasing development of economy in Sichuan and Southwest region, the demand of natural gas is getting more and more. However, gas reservoirs in Sichuan Basin are characterized by low permeability and tight. There are plenty of low permeability and extremely low permeability reservoirs. More than one third of reserves belong to low permeability and extremely low permeability reserves among the existing residual recoverable reserves. In general, these kinds of gas reservoirs are characterized by complicated development techniques, difficult producing reserves, poor stable-production condition, low production in single well and bad comprehensive production efficiency. In order to solve the problem of development of low permeability in Sichuan Basin, this paper adopt some techniques and theories such as seismic, well logging, reservoir engineering, percolating mechanics, numerical simulation and laboratory research to perform the theoretical, experiment and application researches including reservoir characteristics, percolating mechanism, analysis method of well test, reservoir reform techniques, reservoir protection techniques and horizontal well as well as unbalanced drilling techniques in low permeability reservoir. A set of development technical system has been formed adapting to carbonate and sandstone in low permeability reservoir in Sichuan, which has laid a stable foundation for efficient development of low permeability reservoir in Sichuan. The major research results are as follows:1. On the foundation of research for reservoir lithology, characteristics of pore structure, type and distribution of fracture of typical low permeability reservoir in Sichuan, taking the parameters of physical property, type and structure of pore as major quantitative basis, and with comprehensive.consideration of degree of fracture growth and its important role in the reservoir permeability, this paper has advanced the method of low permeability reservoir ofdividing into low permeability and extremely low permeability .which accord with the fact of low permeability reservoir in Sichuan.2. his is the first time to establish percolating pattern of the quartemary percolating channel for low permeability reservoir composed of macrofracture, fine fracture and microfracure as well as pore throat. And the matrix pore throat and microfracture are the foundations of storage and percolating in reservoir. The reservoir productivity and percolating characteristics depend on the correlation of the quarternary percolating channel. The pattern is significant to development of low permeability reservoir.3. For the characteristics of low permeability reservoir, the paper have made good use of reservoir techniques including structure analysis, seismic inversion and pattern recognition and proposed a set of fracture and reservoir lateral predictions method and techniques including the comprehensive evaluation index of fracture growth, which improve and develop reservoir evaluation and favorable block's prediction in low permeability reservoir. Remarkable results have been gained in the prediction in fracture and pore growth areas of Xu2 in Pingluoba, Carboniferous reservoir of Wubaiti and Penglaizhen Formation in Baima-Songhua.4. Overall and thorough experiment research for low-velocity non-Darcy percolating mechanism has been made under single phase gas and residual water in low permeability, and low-velocity non-Darcy percolating characteristics have been realized. The result is instructive...