页岩压裂裂缝气测导流能力实验研究

页岩遇水容易膨胀以及实际生产时页岩气并不含水,液测导流能力并不能真实反映页岩气在地层裂缝中的渗透能力。压裂用支撑剂多是以钢板夹持支撑剂、蒸馏水为驱替流体完成测试,由于钢板表面平滑、刚性不可嵌入,无法反映页岩储层裂缝壁面不规整、支撑剂在页岩壁面特性,蒸馏水属于液相介质,无法反映天然气气相流动,因此需要改进实验方法。通过对API标准的导流室改进后,采用露头页岩岩心加工成的岩板模拟储层人工裂缝,氮气模拟天然气在页岩岩板夹持下的气相流动,测试其导流能力,优化铺砂浓度。理论分析认为,支撑裂缝只要有一定的宽度,其渗透率仍远高于页岩基质的渗透率。气测裂缝导流能力结果能够真实反映地层情况,为铺砂浓度优选和页岩气藏压裂设计施工等提供可靠依据。

Experiment Research on Fracture Conductivity of Shale Based on Gas Logging

Shale is easy to swell while it contacting water, and shale gas in the actual production does not contain water, the conductivity obtained by liquid logging cannot truly reflect the permeability of shale gas in cracks of the formation. The fracturing support agent is tested by using the steel plate to hold the supporting agent, and distilled water as the displacement fluid; the steel plate has smooth surface, and is not embeddable due to the rigidity, so it cannot reflect the shale reservoir fracture whose surface is irregular; distilled water is liquid medium, so it can not reflect the natural gas flow, therefore the experimental method needs to be improved. Through improving the diversion chamber of the API standard, artificial fractures in the reservoir was simulated by using outcrop shale cores, gas flow of natural gas in the gas phase of the shale rock plate was simulated by nitrogen gas, and the flow conductivity was tested, sand concentration was optimized. Theoretical analysis shows that, as long as there is a certain width of the crack, its permeability is still much higher than the permeability of the shale matrix. The results of gas flow measurement can reflect the formation conditions.