塔河油田奥陶系油藏开发动态与地层水化学特征响应

Development Performance of Ordovician Reservoir and Hydrochemical Response in the Tahe Oilfield

塔河油田是塔里木盆地第一个超亿吨级的大型油田,其主力油藏为奥陶系缝洞型碳酸盐岩油藏。近年来,油田地层水的问题日益突出,严重影响了油田的开发和生产。阿克库勒凸起北部地质历史时期曾经发育间断性的大气水下渗—向心流,凸起南部斜坡区受到泥岩压实排水和粘土矿物脱水形成的离心流的影响,地层水受到一定程度的淡化。塔河油田主体部位处于越流泄水区,地层水具有明显的高矿化度和高K++Na+、Cl-浓度,有利于油气聚集成藏。塔河油田奥陶系地层水动力场形成演化与油气运移、聚集密切相关。海西晚期、喜马拉雅期离心流强度大,是油气藏主要成藏期。早、晚海西运动、印支运动期间抬升剥蚀,遭受强烈的大气水下渗淋滤、生物降解,是油气藏主要破坏期。根据地层水赋存状态,区分出洞穴底部油气驱替残留水、洞穴周缘小缝洞系统驱替残留水、储层下部层间水3种不同类型。研究油井产出水矿化度、Cl-、K++Na+浓度动态变化规律,总结出平稳型、起伏型、上升型和下降型4种动态类型。通过综合分析油井开发动态及油水产出特征,正确把握其变化过程,可以判断油井产水来源,从而为油田的稳油控水提供指导性建议。

Tahe oilfield is one of the first oilfields with over one hundred million tons of reserve. The main reservoir is a fracture-cave type reservoir in the Ordovician carbonate formation. Recently, the formation water is becoming problematic and severely impacting the development and production of the oilfield. Horizontally, a fresh water zone due to meteoric water can be found in the north part of Akekule heave. A marginal freshening zone caused by water released from mudstone compaction is found at the bottom of southern slope. Located in the cross-formational flow discharge zone caused by the centripetal and the centrifugal flow, the primary Tahe oilfield, featured by high salinity and concentration of Cl-and K^＋ ＋ Na^＋ , is favorable for accumulation of hydrocarbon. The formation and evolution of hydrodynamic field in Tahe oilfield are closely related to the migration and accumulation of oil and gas. The centrifugal flow is great during late Hercynian period and Himalayan period, which is main stage of hydrocarbon formation. Strong meteoric water infiltration and leaching as well as biodegradation occurred during early Hercynian movement, late Hercynian movement and Indosinian movement, which is main stage of hydrocarbon destruction. According to the occurrence of water, three types of formation water： residual water in bottom of cave after oil and gas displacement, residual water in fracture and vug around cave after oil and gas displacement and interlayer water under reservoirs, were identified in this paper. Based on the study of variation trends of total mineralization, Cl-and K^＋ ＋Na^＋concentrations in produced water, four dynamic types were summarized： stationary type, fluctuating type, rising type and declining type. According to the development performance of oil well and production of oil and water, the source of produced water can be identified, which can guide for controlling water and stabilizing the oil production under different circumstance in Tahe oilfield.