冲积扇背景下的砂体沉积类型及优势储集砂体

SAND-BODY SEDIMENTARY MODES AND FAVORABLE RESERVOIR SAND BODIES OF ALLUVIAL FAN

依据测井、岩心资料，对准噶尔盆地西北缘乌尔禾油田百口泉组进行了砂体沉积类型划分。在冲积扇相-扇中、扇缘亚相背景下，研究区沉积物类型主要为筛状沉积、辫状河道沉积、片流沉积、泥石流沉积4种。辫状河道沉积呈明显的正韵律，具板状、槽状交错层理，富含油；筛状沉积呈微弱的反韵律，层理构造不发育，多为块状构造，含油级别较辫状河道低。在此认识基础上，明确了乌尔禾油田百口泉组地层储集砂体厚度分布特征，对优势储集砂体通过实例剖面进行了量化认定，最终确定优势储集砂体类型，优势储层为辫状河道砂体，筛状沉积为次要储层，泥石流沉积仅局部发育在东部WU7井一带，未见油气显示。在此优势储集砂体分布规律指导下部署钻探的13口评价井均在T1b^2、T1b^3段见到了良好的油气显示，有效指导了油田现场勘探开发。

Based on the well testing and core data, the sand-body sedimentary modes of Baikouquan Formation have been classified in Wu＇erhe oilfield located near the northwest margin of Junggar basin, and under the background of alluvial fan-middle fan and fan margin subfacies, 4 main types of the sediments in the studied area have been determined, including sieve-shaped deposition, braided river channel deposition, laminar flow deposition and mud flow deposition. The braided river channel deposition presents obvious normal rhythm, tabular cross and trough cross beddings, and is usually oil-rich; while the sieve-shaped deposition presents weak inverted rhythm, undeveloped beddings and block tectonics, and the oil-bearing degree of which is lower than that of braided river channel deposition. Based on the above understandings, the reservoir sand-body thickness distribution features have been determined in Baikouquan Formation of Wu＇ erhe oilfield and the favorable reservoir sand-body types have been identified through quantitative analysis on the cross sections of case study, obtaining the result that braided river channel sand body belongs to favorable reservoir sand body and sieve-shaped deposition belongs to less important reservoirs. The mud flow deposition exists locally in the east near Well No. WU7 and there are no oil or gas shows. Under the guidance of distribution laws of the favorable reservoir sand bodies, 13 appraisal wells have been drilled and all have achieved good oil and gas shows in intervals T1 b^2 and T1 b^3, which mean these have effectively assisted the oilfield exploration and development.