A rock-based geologic characterization was completed on a continuous core through the Austin Chalk Group section, an active exploration target in southern Texas. Because this core (located in the Pearsall field) is continuous and includes both lower and upper contacts, it can be used as the type cored section for the southern Texas Austin Chalk. Several general lithofacies are defined. Two lithofacies (lithofacies 1 and 2) are highly bioturbated and have low to moderate organic matter content and are poor to moderate source rocks. Two other lithofacies (lithofacies 3 and 4) are laminated, lithofacies 3 containing some burrows and lithofacies 4 containing no burrows. Both lithofacies are good source rocks. Organic matter in the laminated lithofacies 3 and 4 and some of the organic matter in the bioturbated lithofacies 2 are dominated by type II kerogen, suggesting the section can be self-sourcing. A general trend is observed whereby lithofacies that were deposited under more-oxygenated conditions increase in abundance up section and is related to a decrease in total organic carbon and, hence, source-rock quality. The primary oil and gas production is from fractures with possible later production from the nano- to microporous matrix after pressure drawdown. Pore types are predominantly interparticle nano- to micropores and lesser intraparticle nanopores as defined by Loucks et al. (2012). Porosity is less than 8%, and permeability is less than 0.05 md and ranges down into the nanodarcy range. The type cored section adds to the understanding of the southern Texas Austin Chalk by providing a geological description of lithofacies, stacking patterns, source-rock quality characterization, and reservoir quality. The type core can be used as a comparison section to other cored sections of the Austin Chalk.

中文翻译：

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德克萨斯州南部上白垩统奥斯汀白垩群类型取芯剖面的地质特征：裂缝性和非常规油藏组合

通过奥斯汀白垩组部分的连续岩心完成了基于岩石的地质特征，这是德克萨斯州南部的一个活跃勘探目标。由于该岩心（位于 Pearsall 油田）是连续的，并且包括上下触点，因此它可以用作德克萨斯州南部奥斯汀粉笔的类型取芯部分。定义了几种一般岩相。两个岩相（岩相 1 和 2）高度生物扰动，有机质含量低至中等，烃源岩贫至中等。另外两个岩相（岩相 3 和 4）是层状的，岩相 3 包含一些洞穴，而岩相 4 不包含洞穴。两种岩相都是良好的烃源岩。层状岩相 3 和 4 有机质和生物扰动岩相 2 的部分有机质以 II 型干酪根为主，表明该剖面可以自采。观察到的一般趋势是，在更多含氧条件下沉积的岩相在剖面上的丰度增加，并且与总有机碳减少有关，因此与烃源岩质量有关。主要的石油和天然气生产来自裂缝，随后可能在压力下降后从纳米到微孔基质生产。孔隙类型主要是由 Loucks 等人定义的颗粒间纳米到微孔和较小的颗粒内纳米孔。(2012)。孔隙率小于 8%，渗透率小于 0.05 md，范围低至纳达西范围。类型取芯剖面通过提供岩相、堆积模式、源岩质量特征和储层质量的地质描述，增加了对德克萨斯州南部奥斯汀白垩区的理解。类型核心可用作与 Austin Chalk 其他核心部分的比较部分。