新疆克拉玛依油田一中区克拉玛依组辫状河储层砂体类型及分布特征

通过露头实测、岩心观察及测录井资料分析等结果表明,克拉玛依油田一中区克拉玛依组S7、S5和S4砂层组沉积时期以发育辫状河为特征,可进一步划分为近源砾质辫状河、远源砾质辫状河和砂质辫状河沉积3种类型。上述3种类型的辫状河沉积在沉积特征、河道空间叠置样式及组合关系等方面存在明显的差异。近源砾质辫状河河道岩性以砾岩为主,为中孔低渗储层。单河道沉积厚度2~4.5m,宽度500~800m,表现为河道-河道直接接触的连片组合方式;远源砾质辫状河河道岩性仍以砾岩为主,含少量砂岩,物性较近源砾质辫状河略好,为中孔低渗储层。单河道沉积厚度为1.5~4m,河道砂体宽度400~750m,表现为河道-溢岸-河道的连片组合方式;砂质辫状河河道岩性以砂岩为主,为中孔低渗储层,物性优于砾质辫状河。单层厚度为0.5~2.5m,宽度为300~700m,但河道沉积分布范围有限,河道之间多为带状或交织带状组合方式。根据上述对比分析认为砾质辫状河河道砂体虽然物性相对较差、非均质性较强,但砂体厚度大、分布广泛、连通性好,目前为全区主要油气开发的目的层;砂质辫状河河道砂体尽管物性较好,但由于厚度较薄,分布局限,仅在东部地区其累计厚度较大,当与其它成藏条件匹配时,可形成具有开发潜力的目的层。

Types and distribution of the braided channel reservoir sandstones in the Karamay Formation in Quadrant 1 of the Karamay Oil Field, Xinjiang

The integration of outcrop measurement, core observation and well logs show that the braided channel deposits were developed during the deposition of the S₇, S₅ and S₄ sandstone measures in the Karamay Formation in Quadrant 1 of the Karamay Oil Field, Xinjiang, and may be classified into three types of proximal gravelly braided channel deposits, distal gravelly braided channel deposits and sandy braided channel deposits. Lithologically, the proximal gravelly braided channel deposits are mainly made up of conglomerates, with subordinate sandstones, and have medium-sized porosity and low permeability. A single channel has the sedimentary thickness varying from 2 to 4.5 m and a width from 500 to 800 m, and displays the distribution patterns as the channel-channel associations. The distal gravelly braided channel deposits are the same as the proximal gravelly braided channel in lithology. A single channel has the sedimentary thickness varying from 1.5 to 4 m and a width from 400 to 750 m, and constitutes the distribution patterns as the channel-overbank-channel associations. The sandy braided channel deposits are dominated by the sandstones and occur as medium-sized porosity and low-permeability reservoirs. A single channel has the sedimentary thickness varying from 0.5 to 2.5 m and a width from 300 to 700 m, and constitutes the distribution patterns as the banded or interbanded associations. The positive aspects of the gravelly braided channel sandstones are relatively thick reservoir sections, extensive and well-connected sandstone reservoirs, and thus may be considered as the main target for the petroleum exploration throughout the study area.