LONG ISOLATION INTERVAL CEMENTING PRACTICE IN WELL QIUDONG-27

Cementing isolation interval usually ranges between 800~1200m,while in Well Qiudong-27,3125m long of isolation interval is required due to faulted structure and complex downhole conditions,which makes the operation extremely difficult.For long isolation cementing,due to the large temperature difference between the downhole flowing temperature and the static temperature at the cement top,poor cementation will be caused,and this severely affected the cementing quality;at the same time,long isolation cementing will also increase the bottomhole hydraulic pressure remarkably,thus cause lost circulation during cementing.Large scale of laboratory tests were conducted,and 2 types of cement slurry systems were selected for cementing;specifically,light weight slag slurry of wide temperature range was selected for the upper interval,while conventional cement slurry was used for the lower interval,and proper cementing measures were adopted.The cementing job for this well was successful,and excellent cementing quality was achieved.