Abstract:

The drilling geological profile of Well-JY1 Wufeng Formation and Longmaxi Formation is the first systematic marine shale gas parameter well profile. The exploration breakthrough of Well-JY1 announces the discovery of Fuling shale gas field, which is named as“Shale Gas Development merit well” by Chongqing Fuling Municipal government. With the drilling geological section in Wufeng-Longmaxi Formation of Well-JY1 as the key point, the drilling profiles of the importance of shale gas exploration and development are expounded, the profile lithostratigraphic, biostratigraphic and graptolite biozone division and fracture development characteristics are introduced, and analyzed the period of “six”shale gas reservoir characteristics and vertical distribution are analyzed. The following conclusion are obtained. Firstly, the Wufeng-Longmaxi Formation in Well-JY1 has large thickness, continuous deposition, clear stratigraphic sequence, widest range of graptolite category and good regional comparability, which can be used as the basic drilling geological section for the analyses and researches of Wufeng-Longmaxi Formation in Sichuan Basin and its surrounding areas. Secondly, affected by sedimentary facies belt, the geological characteristics of different shale gas strata are obviously different. For example, the first interval of the first Member of Wufeng-Longmaxi Formation（small layer ①~⑤）, which belongs to the deep-water shelf facies generally with four high characteristic of “high TOC, high porosity, high air content, high siliceous”, is the main “sweet spot” of the shale gas exploration and development in this area. Thirdly, the small layer ①~③ in high quality shale gas reservoir, which show the high coupling law of double “sweet spot” of geological and engineering, are the optimal layers for the best target “window” of the horizontal wells. Among them, the small layer ② with high gamma value is the best position to ensure the horizontal trajectory and drilling ratio of high quality shale. The determination of high quality shale and the target “window” in deep-water shelf facies is the key for the major breakthrough of shale gas exploration in Wufeng-Longmaxi Formation of Well-JY1 and the continuous stable and high production, and also points out the direction for the selection of the areas and layers during the subsequent shale gas exploration.

Key words: Well-JY-1, shale gas, geological section, Wufeng-Longmaxi Formation, Sichuan Basin