Pore types and pore-size distributions across thermal maturity, Eagle Ford Formation, southern Texas
Pore types and pore-size distributions across thermal maturity, Eagle Ford Formation, southern Texas
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DOI：
10.1306/03051514151
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发表时间：
2015-09-01
期刊：
影响因子：
3.5
通讯作者：
Milliken, Kitty
中科院分区：
文献类型：
--
作者：
Pommer, Maxwell;Milliken, Kitty
德克萨斯州南部 Maverick 盆地 Eagle Ford 地层的孔隙类型、孔径和孔隙丰度随着热成熟度的变化而系统地变化。使用来自 4 口井的 20 个样品的扫描电子成像来评估孔隙对化学和机械过程的复杂响应，包括原生孔隙度的破坏和次生孔隙的产生。原生矿物相关孔隙因次生有机质的压实、胶结和填充而被破坏，而次生孔隙则在有机质 (OM) 内生成。早期埋藏期间原生孔隙的破坏（R-o 接近 0.5%）是由于韧性碎屑 OM 和粘土的压实而发生的，在较小程度上是由于次生 OM 的胶结和填充而发生的。较大的孔隙与石珊瑚碎片有关。主要的 OM 是空间上孤立的碎屑 OM“纵梁”。孔隙度在体积上占主导地位（平均 6.2%），主要是相对较大的颗粒间矿物相关孔隙（中值尺寸 51.6 nm [0.000002 in.]；检测限接近 3-4 nm [0.00000012-0.00000015 in.]）。在低成熟度时，孔隙度和孔径与方解石丰度直接相关，与 OM 体积成反比。在较高成熟度时，通过胶结、次生 OM 填充和更大的压实作用，原生孔隙会受到进一步破坏。与矿物相关的孔隙在高成熟度时存在（R-o 类似于 1.2%-1.3%），但与低成熟度相比较小（中值尺寸 30.2 nm [0.0000011 in.]）且丰度较低（平均为 2.5%）。高成熟度样品中的大部分 OM 起源于成岩作用，并已渗透到原生孔隙空间中，覆盖胶结物晶体并填充颗粒内孔隙。大量与矿物相关的孔隙度局部存在于未发生次生有机质侵入原生孔隙空间的样品中。当有机质成熟进入湿气窗口时，会产生大量的次生孔隙度。大多数高成熟度样品中的孔隙度在体积上主要由较小的 OM 托管孔隙（中值尺寸 13.2 nm [0.00000051 in.]）主导（平均为 1.3%）。
Pore types, pore size, and pore abundance vary systematically across thermal maturity in the Eagle Ford Formation, Maverick Basin, southern Texas. Scanning electron imaging of 20 samples from four wells is used to assess the complex response of pores to chemical and mechanical processes, entailing both destruction of primary porosity and generation of secondary pores. Primary mineral-associated pores are destroyed by compaction, cementation, and infill of secondary organic matter, whereas secondary pores are generated within organic matter (OM).Destruction of primary pores during early burial (to R-o similar to 0.5%) occurs by compaction of ductile detrital OM and clays and, to a lesser degree, as a result of cementation and infill of secondary OM. Larger pores are associated with coccolith debris. The dominant OM is spatially isolated detrital OM "stringers." Porosity is volumetrically dominated (average 6.2%) by relatively large, mostly interparticle mineral-associated pores (median size 51.6 nm [0.000002 in.]; detection limit near 3-4 nm [0.00000012-0.00000015 in.]). At low maturity, porosity and pore size correlate directly with calcite abundance and inversely with OM volumes.At higher maturity, further destruction of primary pores occurs through cementation, secondary OM infill, and greater compaction. Mineral-associated pores are present at high-maturity (R-o similar to 1.2%-1.3%), but are smaller (median size 30.2 nm [0.0000011 in.]) and less abundant (average of 2.5%) than at low maturity. A large portion of OM within high-maturity samples is diagenetic in origin and has pervaded into primary pore space, coating cement crystals, and filling intraparticle pores. Substantial mineral-associated porosity is locally present in samples where incursion of primary pore space by secondary OM has not occurred.Abundant secondary porosity is generated as OM matures into the wet-gas window. Porosity in most high-maturity samples is volumetrically dominated (average of 1.3%) by smaller, OM-hosted pores (median size 13.2 nm [0.00000051 in.]).