缝洞性碳酸盐岩油气藏开发对策——以塔河油田主体开发区奥陶系油气藏为例

Development strategy of fractured-vuggy carbonate reservoirs—taking Ordovician oil/gas reservoirs in main development blocks of Tahe oilfield as examples

塔河油田奥陶系油气藏是典型的古岩溶缝洞性碳酸盐岩油气藏,开发初期采取滚动勘探开发模式、分批次动用储量、“点、线、面”复合直井井网控制储量、以地震属性的提取与分析为主的储层预测与识别技术、深度酸压和侧钻水平井等技术取得了较好效果,使开发井建产成功率由不足60%提高到85%以上,探明石油地质储量突破5×108t,油田年产量达到350×104t。随着开发进程的深入,对缝洞储集体的识别精度不够,缝洞性油藏储量的可信度低,开发中后期缺乏提高采收率和单井产能的对策等方面影响了开发效果的进一步提高。为此,下步的开发工作中应采取以下措施:1)以动用储量或可采储量作为开发方案编制或调整的依据;2)用直井加水平井的复合井网增加对储量的控制;3)重新划分开发单元;4)采用单井控制储量规模确定合理开发井数;5)以合理生产压差确定单井配产。

Ordovician reservoirs in Tahe oilfield are typical fractured-vuggy carbonate reservoirs of fossil karst type. Progressive exploration and development pattern was adopted in the initial stage of development. Reserves were brought into production stage by stage. Vertical well pattern combining the selected “spots, lines and the whole area” was applied to control the reserves. Reservoir prediction and identification technologies with extraction and analysis of seismic attribute as the core, as well as strong acid fracturing and sidetrack horizontal drilling technologies were successfully applied in development. Success ratio of development well increased from below 60% to over 85%, discovered oil reserves in place exceeded 500 million tons, and annual production capacity of the oilfield reached 3.5 million tons. However, several factors have influenced further improving development effects along with progress of oilfield development, such as inadequate understanding of the features of fractured-vuggy reservoirs, low reliability of discovered oil reserves, and lack of measures to enhance oil recovery and single well production capacity in mid-and late-development stages. To solve these problems, the following measures should be taken in future oilfield development： （a） compilation or adjustment of development program should be made on the basis of producing reserves or recoverable reserves; （b） enhancing control over reserves by applying combined vertical and horizontal well pattern; （c） redividing development blocks; （d） determining rational well numbers according to single well controlled reserves; and （e） determining individual well＇s production proration according to rational producing pressure drop.