阿姆河盆地卡拉库里区块侏罗系油气地质条件分析

卡拉库里区块位于阿姆河盆地北部的查尔朱阶地上,勘探目的层为上侏罗统卡洛夫阶—牛津阶碳酸盐岩。烃源岩以下—中侏罗统滨海-三角洲相沉积的深灰色泥岩、碳质泥岩和煤层为主,有机质丰度中等—好,腐泥-腐殖型和腐殖型,进入成熟阶段,具备一定的生烃潜力,区块所在的查尔朱阶地正好位于烃类运移的指向上,有利于烃类的聚集。上侏罗统卡洛夫阶—牛津阶台地相沉积的鲕粒灰岩、砂屑灰岩是区块内的主要储层,储集空间为粒间溶孔、铸模孔和压溶缝,储层以低孔低渗为主,但在裂缝的配置下,储集性能较好。上侏罗统碳酸盐岩的层间水的矿化度高,成因系数值rNa/rCl和rCa/rMg分别为0.7和3.5,地下水处于停滞的还原环境,上侏罗统启莫里阶—齐顿阶膏盐层厚度大且广泛分布,封闭性好,有利于油气保存。根据区块构造解释成果,研究区主要发育低幅背斜圈闭,圈闭的形成时间与油气运移时间配置关系合理,预测油气富集区主要位于区块南部的背斜构造带上。

Analysis of Petroleum Geological Characteristics of the Jurassic in Karakul Block,Amu-Darya Basin

Karakul Block located in Chardzhou terraces of Amu-Darya Basin in Uzbekistan. The main exploration target is Jurassic Callovian-Oxfordian carbonate rocks. The source rocks are dark gray mudstone, carbon mudstone and coal deposited in the Lower-Middle Jurassic coastal-delta facies, with middle-good organic abundance, sapropel-humic and humic organic types as well as mature generation stage and has potential to generate hydrocarbon. The Chardzhou terraces is located in the direction of the hydrocarbon migration and favourable for the oil and gas to be accumulated. The types of reservoir rocks are mainly Callovian-Oxfordian carbonate rocks, including oolitic limestone, calcarenite, and its reservoir spaces consists of intragranular dissolved pore, mould pore and solution stylolite. The carbonate reservoirs is of low porosity and low permeability, but if fractures were relatively developed, the carbonate rocks are in good reservoir property. The formation water in the Upper Jurassic carbonate rocks is high mineralized and the ratio of Na/ Cl and Ca/ Mg were 0.7 and 3.5 , which indicate the weak reduction environment. Moreover, the large thickness, widely distributed gypsum-salt deposited in Kimmeridgian-Tithonian tidal flat-lagoon facies as cap rocks, are favourable for gas accumulation and preservation. On the basis of structural interpretation of Karakul Block, the main trap style is low amplitude anticlinal structure.The forming times of traps and hydrocarbon generation,migration matched rationally. The potential plays mainly occur in the anticline belts in the sourth of Karakul Block.