含体腔孔生物碎屑混积岩初始孔隙度恢复方法—以环渤中地区沙一二段混积岩储层为例
- 收稿日期:
2023-11-23
- 网络出版日期:
2024-03-04
摘要: 【目的】环渤中地区古近系沙河街组一二段发育混积岩储层且富含有大量油气资源，其中腹足类生物碎屑富集，其特有的生物体腔孔使得混积岩初始孔隙度不能以常规碎屑岩初始孔隙度恢复公式求取，目前国内外尚缺少混积岩初始孔隙度的恢复方法，而初始孔隙度的准确恢复是研究储层演化的关键内容。【方法】选用现代螺类样品，通过实验法和公式法分别求取螺类生物体腔孔体积，然后再通过构造物理模拟实验模拟螺类生物体腔孔在真实沉积环境中的充填情况，最后以前人常用的储层初始孔隙度计算公式为基础，得到一种适用于混积岩储层的初始孔隙度计算公式。【结果】研究表明：螺的种类是影响螺类生物体腔孔体积占比的最大因素。不同种类的螺，有效储集空间即体腔孔孔隙度的大小不同；影响同一种螺体腔孔孔隙度差异的原因主要为体腔孔腔口的大小。以生物碎屑含量较高的QHD36-3-A井3765.03m混积岩样品为例，求得该深度混积岩的初始孔隙度为51.68%左右。【结论】本文以前人公式为基础，结合物理模拟实验建立了一个新的求取混积岩初始孔隙度的计算方法，对于混积岩储层演化研究具有重要意义。
Method for Restoring the Initial Porosity of Bioclastic Mixed Rocks with Body Cavities: A Case Study of Mixed Rock Reservoirs in the Es12 Formation Around Bozhong Sag, Bohai Bay Basin
- Received Date:
2023-11-23
- Available Online:
2024-03-04
Abstract: [Objective] The Paleogene Shahejie Formation around the Bozhong sag, Bohai Bay Basin is characterized by the development of mixed rock reservoirs, which are rich in abundant oil and gas resources. The unique biomass cavity pores in mixed rock reservoirs make the initial porosity of mixed rocks cannot be obtained by the conventional initial porosity recovery formula for mixed rocks, and there is a lack of initial porosity recovery methods for mixed rocks both at home and abroad, and the accurate recovery of the initial porosity is a key element in the study of the evolution of the reservoir. [Methods] In this study, modern snail samples were selected to determine the volume of snail body cavities using experimental and formulaic methods. Subsequently, a physical simulation experiment was conducted to simulate the filling conditions of snail body cavities in a real depositional environment. Finally, based on commonly used formulas for calculating initial porosity in reservoirs, a formula suitable for mixed rock reservoirs was derived. [Results and Discussions] Studies have shown that the species of snails is the biggest factor affecting the percentage of body cavity pore volume of snails. Different species of snails have different sizes of effective storage space, i.e., body cavity pore porosity; the main reason affecting the difference in body cavity pore porosity of the same species of snails is the size of the body cavity pore lumen. Taking the mixed rock sample from well QHD36-3-A at a depth of 3765.03m with a high content of fragmented bioclasts as an example, the initial porosity of this mixed rock at that depth was determined to be 51.68%. [Conclusions] In this paper, a new calculation method to find the initial porosity of mixed rocks is established based on the previous formula and combined with physical simulation experiments, which is of great significance for the study of mixed reservoir evolution.
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