Fula油田稠油油藏地层出砂机理实验研究

A laboratory research for the sand-production mechanism of viscous oil reservoirs in Fula oil field

苏丹 6区Fula油田稠油油藏的主要产层Bentiu组和Aradeiba组出砂严重。为了采取适当的防砂措施 ,用Bentiu组的散砂制做成型样品 ,在不同围压条件下进行三轴岩石力学实验。实验结果表明 ,Bentiu组砂岩内聚力很小 (1.5MPa) ,在较小的生产压差下就出现内聚强度破坏 ,导致早期出砂 ,此后内聚强度破坏和剪切破坏加剧 ,产砂面会逐步深入地层 ,造成大量出砂 ,所以必须早期防砂 ,同时应控制生产压差投产。图 3参 5 (汪永利摘 )

Fula oil field is a main oil field found in the exploration and development of the 6th zone (Unit 6) of Sudan. It consists of Bentiu Formation and Aradeiba Formation with the crude oil viscosity of 300 500 mPa.s under reservoir condition. Severe sand production occurred during perforation and well testing. To find out the cause of sand production in order to take appropriate sand control measures, rock mechanics experiment research was carried out for Bentiu Formation. Mohr Couloumb failure envelope was obtained through triaxial test under different confining pressure. Tested cylindrical samples were from unconsolidated formation sands. Experimental results showed that cohesion strength of Bentiu Formation sand was very low (1.5MPa) and premature sand production would occur even under low drawdown pressure. So it is not practical by controlling drawdown pressure. In addition, cohesive failure of the formation would finally lead to shear failure as more and more sands were dragged out and severe sand production would start. Therefore,it is necessarg to control the sand produition and producing pressure differential at the early stage of putting oilfield in production.