低弹性模量碳酸盐岩储层裂缝导流能力实验研究

Experimental study on the fracture conductivity in the carbonate reservoirs with low elastic modulus

中东及中亚地区碳酸盐岩储层弹性模量较低,仅为中国碳酸盐岩储层弹性模量的1/2~1/3。这类储层酸压后增产有效期短、裂缝导流能力难于保持。为此开展了室内实验,研究储层弹性模量、排量和酸压工艺对裂缝导流能力的影响。结果表明:对于低弹性模量(<20 GPa)碳酸盐岩来说,采用胶凝酸酸压,在闭合应力超过20 MPa后导流能力无法保持;对于低弹性模量碳酸盐岩,高排量比低排量的导流能力强。高闭合应力条件下,闭合酸化可以有效提高裂缝导流能力,且闭合酸化时低排量注酸导流能力提高效果更好。中东S油田碳酸盐岩酸压后虽然产生大量的酸蚀蚓孔,但没有形成有效的导流能力,采用加砂压裂后导流能力更好。

The carbonate reservoirs in the Middle East and the Central Asia have lower elastic modulus,which is only 1/2-1/3 that in China.After this type of reservoirs is treated with acid fracturing,the effective stimulation period is short and the fracture conductivity can be hardly maintained.In this paper,laboratory experiment was carried out to study the influences of elastic modulus,displacement and acid fracturing technology on the fracture conductivity.The results show that when gelling acid fracturing is applied in the carbonate rocks with low elastic modulus(<20 GPa),the fracture conductivity cannot be maintained after the closure stress exceeds 20 MPa.As for the carbonate rocks with low elastic modulus,the fracture conductivity at high displacement is stronger than that at low displacement.At high closure stress,closed acidizing can improve the fracture conductivity effectively.And in the situation of closed acidizing,the fracture conductivity can be improved better at low-displacement acid injection.After acid fracturing is carried out in the carbonate rocks of S Oilfield of the Middle East,a great number of acid wormholes are generated,but effective fracture conductivity is not formed.And the fracture conductivity gets better after sand fracturing.