RESERVOIR PROTECTION TECHNOLOGY FOR CEMENTING HORIZONTAL WELLS IN BLOCK CAOGU 100

Ten horizontal wells are planed in block Caogu100, which is a buried hill thick oil reservoir in the Caoqiao oilfield, and screen pipe completions are designed. In cementing the ?244.5mm intermediate casing that run through the buried hill reservoir, great contamination is caused by cement slurry, and no notable production improving is found in the first two horizontal wells over the vertical wells. To solve this problem, reservoir protection programs designed for cementing the ?244.5mm intermediate casing are applied with success, and the average production rate increased by 142% per well. The features of buried hill reservoir are described, and the use of two-stage cementing method, continuous open stage collar and cement basket is also presented. The first stage cementing is conducted to isolate the formation above 30m of the cement basket, and the second stage cementing is carried out through the continuous open stage collar only after the setting of the first stage cement. The use of cement basket can keep the cement slurry form impacting the formation directly, which may cause lost circulation and formation damage, and enhances cementing quality therefor.