提高苏丹6区固井质量的柔性水泥浆固井技术

苏丹6区位于苏丹共和国西南部,该区244.5 mm套管固井水泥封固井段包括主力产层,采用常规水泥浆体系固井后,电测水泥环胶结质量均不理想。完钻后,套管试压过程中产生的套管变形,以及继续钻井过程中钻柱和钻头对套管的撞击作用对井壁与套管间水泥环的破坏加大了对固井界面胶结的不良影响,甚至造成水泥环层间封隔失效。为此,在244.5 mm套管固井中引入了一套新的柔性水泥浆体系。该水泥浆体系中混有2%的膨胀剂和2%~3%的增韧剂。膨胀剂中的有效组分在水泥水化过程中促进水泥晶体的晶型变化和体积增加,以补偿水泥水合硬化时产生的体积内收缩,从而有效地消除了水泥石固结过程中产生的微间隙,增韧剂显著提高了水泥石的韧性和抗冲击性,实现了苏丹6区244.5 mm中间套管环空的良好封固,提高了界面的胶结质量。

A flexible slurry system to improve cementing quality at Block 6 in Sudan

At Block 6 in Sudan, Φ244.5 mm cementing section covers main pay zone, but the cement bonding logging (CBL) value of cement sheath cemented by conventional API Class G cement is not as good as expected. The Φ244.5 mm casing deformation during the ultimate casing pressure test and cement sheath damage made between the casing and well wall by the impact of bit and drilling string during continuing drilling produces serious effects on cement bond and even causes zonal isolation failure. To solve this problem, a new kind of flexible slurry system is developed with sweller (2% by weight of cement) and flexibilizer (2~3% by weight of cement). The effective components of the sweller will promote cement crystal pattern change and increase cement crystal volume so as to compensate the inner volumetric shrinkage during cement hydration, and the micro clearance produced during cement setting can be effectively eliminated. And the flexibilizer increases the toughness and impact resistance of set cement. This new kind of flexible slurry made it possible to achieve good bonding at the casing/cement/formation interfaces in the annular of 244.5 mm intermediate casing in Block 6 of Sudan.