Development Techniques for Abnormal High-Pressure Gas Fields and Condensate Gas Fields in Tarim Basin

Abstract

Abstract Tarim Basin is the most hydrocarbon-abundant onshore basin in China. It occupies an important position in "West-to-East Gas Transportation" project. The major force gas fields are of large scale, abnormal high prossure and high productivity of a single well. The condensate gas fields are usually of high formation pressure, high condensate oil content and high pressure of dew point. Through deepening study on the development mechanism and development technologies of the gas fields and condensate gas fields, a series of development technologies in the super-deep and high-pressure gas fields and condensate gas fields in Tarim Basin have come into being in the development practice. The technologies not only have helped to build up Yaha Condensate Gas Field with the largest condensate oil productivity in China, but also have been extensively applied in the early-stage development eveluation of several gas fields in "West-to-East Gas Transportation" project and the comprehensive adjustment of Kekeya Condensate Gas Field. A new model has been created to develop super-deep and high-pressure gas fields and condensate gas fields. Introduction Tarim Basin lies in the south of Xinjiang Uygur Autonomous Region in China. It is a continent drought basin with an area of 56×104km2. It is the most hydrocarbon-abundant onshore basin in China and occupies an important position in "West-to-East Gas Transportation" project. Till the end of 2003, the number of proven gas fields and condensate gas fields had reached 14; the proven natural gas reserves in place was 6224.1×108m3 and the condensate oil reserves in place was 7054.6×104t. The condensate oil reserves ranked in the first position in the onshore oil and gas fields in China. The condensate gas fields in Tarim Basin are usually of high formaiton pressure, high condensate oil content and high pressure of dew point. There are many oil-and-gas bearing formations. The condensate gas reservoirs are distributed from Ordovician to Upper Tertiary. The buried depth of the condensate gas reservoir ranges typically between 3200–5500m while that of the deepest Well KS101 hits 6500m. The initial formation pressure is typically between 40–60 MPa and the pressure coefficient ranges between 1.1–1.2. The formation pressure of Well KS101 is 128.6MPa while the pressure coefficient hits even 2.0. The underground temperature gradient is typically between 1.77–2.78/100m, which is of normal temperature system. The condensate oil content ranges typically between 300–600g/cm3. The condensate gas reservoirs are mostly of approximate saturation and the pressure of the dew point is always 90% higher than the initial formation pressure. Yaha Condensate Gas Field is currently the largest being-developed condensate gas field with a complete geological structure in Tarim, even in China. The proven natural gas reserves in place is 376.45×108m3 and the condensate oil reserves in place is 2975.6×104to. This condensate gas field is a condensate gas reservoir with high wax content, abundant condensate oil and low breakdown pressure difference. Jidike basal sandstone in Upper Tertiary (N1j) in Structure No. 2–3 is layered edge-water condensate gas reservoir while the basal sandstone in Upper Tertiary and the sandstone on th top of Cretaceous (E+K) is massive bottom-water condensate gas reservoir. Kela 2 Gas Field, the major force gas field of "West-to-East Gas Transportation" project, possesses a proven natural gas reserves in place of 2840.3×108m3. It is a gas reservoir with weak edge and bottome water-type anticline block and abnormal high-pressured dry gas. The formation pressure is 74.3MPa and the pressure coefficient is above 2.0. The reservoir is of high gas column, huge depth, steep structure, abnormal high pressure and high productivity of a single well. For developing reasonably and efficiently the gas fields and condensate gas fields in Tarim Basin and providing technological support to "West-to-East Gas Transportation" upstream engineering, a series of development technologies in the super-deep and high-pressure gas fields and condensate gas fields in tarim Basin have come into being in the development practice through deepening study on the development mechanism and development technologies of the gas fields and condensate gas fields.