页岩气裂缝精细预测技术研究及应用——以长宁国家级页岩气示范区为例

Technologies to finely predict fractures in shale-gas reservoirs: An example from Changning National Shale-gas Demonstration Area

基于川南地区的页岩气勘探实践,认为天然裂缝是影响页岩气勘探开发效果的关键因素,对天然裂缝进行预测对于页岩气藏尤为重要。为了更好地指导页岩气开发,以四川盆地长宁国家级页岩气示范区为例,总结了页岩气裂缝精细预测技术及其模型构建,包括:(1)对页岩气裂缝精细预测技术研究及应用主要通过两个方面来实现,一是精细的地震蚂蚁体属性解释,二是精细的地质模型建立;(2)通过建立精细的平台速度场,将时间域的地震解释数据体转化为模型的深度域数据体,建立精细的蚂蚁体地质模型。将该技术应用于长宁国家级页岩气示范区,应用实践证明:(1)将原始地震数据进行构造导向滤波处理可以提高信噪比和构造解释精度;(2)应用likelihood属性进行蚂蚁体追踪可以优化裂缝检测精度,获得更小级别的裂缝响应;(3)勘探实践表明,裂缝精细预测的平均符合率为80%;(4)天然裂缝精细预测可以有效地指导压裂改造的规模、工序、工艺、压裂参数的设置,从而达到提升改造效果和单井产能的目的。

Many shale-gas exploration practices in southern Sichuan Basin reveal that natural fractures are the key factors affecting shale-gas exploration and development. So, it’s quite important to predict natural fractures in shalegas reservoirs. In order to provide better guidance for shale-gas development, some technologies and modeling to finely predict fractures in shale-gas reservoirs were summarized. These technologies were applied mainly from two aspects of both fine attribute interpretation of seismic ant cube and fine establishment of geological model. Moreover, a fine platform velocity field was established to transform seismic interpretation data volume in time domain into data volume in depth domain, and then a fine geological model of ant cube was built. These technologies have been applied to the Changning National Shale-gas Demonstration Area. Results show,(1) when structure-steer filtering processing is conducted on original seismic data, both signal-to-noise ratio and structural interpretation accuracy may be improved;(2) applying Likelihood attribute to ant tracking can optimize an accuracy to predict fractures so as to obtain fracture response with smaller magnitude;(3) most exploration practices also illustrate that a coincidence rate of fine fracture prediction is 80% on average;and(4) to finely predict natural fractures can provide an effective guidance for setting fracturing scale, procedure, process, and parameters, so as to improve both stimulation effect and singlewell productivity.