蚀变火山岩储层孔隙度计算方法研究——以金龙地区蚀变火山岩为例

Study on Calculation Method of Porosity of Altered Volcanic Rocks Reservoir——Taking Altered Volcanic Rocks in Jinlong Area as an Example

火山岩蚀变产生的次生矿物充填储层孔隙,影响储层的测井响应特征,导致储层孔隙度计算困难。为了解决蚀变火山岩储层孔隙度计算的问题,本文以金龙地区石炭系蚀变火山岩为例,采用两种方法研究。方法一:利用测井资料结合岩心薄片、全岩矿物等资料,建立评价火山岩蚀变程度的模型,定量计算火山岩的黏土矿物含量,再利用黏土矿物含量对经验参数计算的储层孔隙度进行蚀变校正;方法二:建立基于ECS测井的变骨架密度模型,结合密度测井计算储层孔隙度。两种方法计算的孔隙度与岩心分析孔隙度对比,平均绝对误差均小于1%,表明了两种方法的可行性,实现了蚀变火山岩储层孔隙度的精确计算。最后对比分析两种方法的应用情况,为火山岩储层的勘探开发提供了技术支持。

The secondary minerals produced by the alteration of volcanic rocks fill the pores and fractures of the rocks, which can influence the log response characteristics, making it difficult to calculate the porosity of the reservoir. In order to solve the problem of porosity calculation of altered volcanic reservoir, taking the altered volcanic rocks of Carboniferous in Jinlong area as an example, the porosity of altered volcanic reservoir was calculated by two methods. Method one: through analyzing the influence of alteration on reservoir physical properties and log response, combined with core slice and whole-rock analysis data, an evaluation model for alteration degree of volcanic rock was established, and the alteration degree of volcanic reservoir was calculated by the model, and then the alteration index was converted to clay mineral content, finally the calculated clay mineral content was used to correct the calculated porosity of volcanic reservoir. Method two: three elements of silicon, iron and titanium measured by ECS log were used to calculate the density of volcanic rocks, and then combined with density logging, the porosity was calculated. The porosity of volcanic rock calculated by the two methods had high accuracy. Compared with core analysis porosity, the average absolute error was less than 1%, showing that the two methods are reliable, and the accurate calculation of porosity of altered volcanic reservoir can be realized. Finally, application of the two methods were compared and analyzed. The paper can provide technical support for the exploration and development of volcanic reservoir.