碎屑岩储层结构模态的定量模型

本文研究了受沉积环境制约的颗粒分选对储集层孔隙结构模态的控制作用,建立了因粒径比和相对含量不同可能形成的单模态、双模态悬浮型和充填型、三模态悬浮型和充填型五种基本结构模态的数学模型.认为双模态和三模态不仅能在砾岩中形成,也能在砂岩中形成;砂岩中常见模态为单模态和双模态,而砾岩中的常见类型为双模态和三模态,同时还建立了不同模态的孔隙度和渗透率的测算公式,并认为单模态的孔隙度主要受排列方式(堆积角θ)的影响,双模态和三模态的孔隙度则与颗粒的相对含量(f_i或f_i^r)有关;渗透率主要受排列方式(θ)、颗粒大小(R_i)和相对含量(f_i)三个因素的影响.所建立的数学模型可定量预测不同岩性的孔隙结构模态、物特性征、孔喉大小及其他孔隙结构参数.

QUANTITATIVE MODELS FOR PORE STRUCTURES OF CLASTIC SEDIMENTARY ROCKS

The physical properties and the pore structure of a clastic sedimentary rock are affected by the size and the sorting of the grains, and the models of packing types, i. e, structure model. In this paper how the sorting of grains, one of the important sedimentary environment indexes, affects the type of pore structure model is studied. Five basic structure models have been presented mathematically and geologically according to the sorting of the grain sizes and their relative contents. They are unimodel, floated-bimodel, infilled-bimodel,floated-trimodel and infilled-trimodel. The bimodel and trimodel exist not only in conglomeratic sendstone but also in conventional sandstones. however, the conditions to form different models are dif ferent, and their lithology and pore structure are presented in the photographs attached. Finally, the equations for calculating the porosity and permeability in different structure models have been given. Main results of this study are: l)the porosity is affected only by the packing type(packed angle)in unimodel,while by relative contents of different grains also the bimodels and trimodels; 2) the permeability is affected by packing type, grain size and their relative contents. The mathematic models presented in this paper can be used to predict the structure models in different sedimentary environments to estimate their porosity and permeability,and the size of pores and throats etc., and other parameters of pore structure also.