四川盆地高石梯地区震旦系灯影组气藏高产井地震模式新认识

四川盆地震旦系灯影组为一套主要受沉积和岩溶作用控制的缝洞型储层,以缝洞尺度小、地层岩性复杂、储层纵横向非均质性强等为特征,致使储层钻遇率较低、单井天然气产能差异较大。为了解决该区储层地震识别存在多解性的难题,在对位于乐山—龙女寺古隆起南翼的高石梯潜伏构造区灯四段进行地层精细划分的基础上,结合气井测井、测试资料确定储层组合类型,利用高分辨率地震资料开展了不同储层组合类型典型井的地震响应特征及高产井地震模式研究。结果表明,该区灯四段可划分为3种储层组合类型,对应于3类地震模式:(1)Ⅰ类地震模式,具有"宽波谷+双亮点"或"宽波谷+复波"地震响应特征,缝洞发育,为开发阶段首选的高产井地震模式,可实施大斜度井或水平井工艺;(2)Ⅱ类地震模式,具有"宽波谷"地震响应特征,缝洞较发育,为中产井模式,可实施大斜度井工艺;(3)Ⅲ类地震模式,具有"宽波谷+亮点"地震响应特征,缝洞欠发育,为较低产能井模式,可实施水平井工艺。该地震模式新认识的现场应用效果表明,储层钻遇率超过60%,已完成的8口井平均测试天然气产量高达75.34×104 m3/d。结论认为,基于地震相、缝洞预测及靶体设计一体化的高产井地震模式,支撑了该区天然气勘探开发井位部署和钻井轨迹调整,取得了良好的应用效果。

New understandings of the seismic modes of high productivity wells in the Sinian Dengying Fm gas reservoirs in the Gaoshiti area,Sichuan Basin

The Sinian Dengying Fm in the Sichuan Basin is a set of fractured-vuggy reservoirs mainly dominated by sedimentation and karstification, and characterized by small fractures and vugs, complex stratigraphy and lithology, and strong vertical and lateral reservoir heterogeneity. As a result, the drilling rates are lower and single-well gas productivity varies greatly there. And the reservoir identification results based on seismic data in this area are ambiguous. In view of this, the Deng 4 Member in the Gaoshiti buried structure on the southern flank of the Leshan–Longnüsi palaeohigh was precisely divided in stratigraphy. Then, the types of reservoir assemblages were determined based on gas well logging and test data, and the seismic response characteristics of typical wells with different types of reservoir assemblages and the seismic modes of high productivity wells were studied by using high-resolution seismic data. It is indicated that the Deng 4 Member in this area is divided into three types of reservoir assemblages, which correspond to three seismic modes. Seismic mode Ⅰ: It presents the seismic response characteristics of "wide wave troughs + double highlights" or "wide wave troughs + complex waves", indicating that fractures and vugs are developed. It is the preferred seismic mode of high productivity wells in the stage of development. In this mode, the technology of highly deviated wells or horizontal wells can be implemented. Seismic mode Ⅱ: It presents the seismic response characteristics of "wide wave troughs", indicating that fractures and vugs are relatively developed. It is the mode of moderate productivity wells. In this mode, the technology of highly deviated wells can be implemented. Seismic mode Ⅲ: It presents the seismic response characteristics of "wide wave troughs + highlights", indicating that fractures and vugs are underdeveloped. It is mode of low productivity wells, in which the technology of horizontal wells can be implemented. The new understandings on seismic modes were applied on site. It is shown that the reservoir drilling rate is over 60% and the average gas production rate during the production test of 8 wells is up to 75.34×10⁴ m³/d. It is concluded that the seismic mode of high productivity wells based on seismic facies, fracture and vug prediction and integrated target design provides a support for the well arrangement and drilling trajectory adjustment in natural gas exploration and development in the Gaoshiti area and good results have been achieved.