Preparation and application of organic positive gel-polymer drilling fluid

The properties of drilling fluid for drilling horizontal side-_tracked slim hole were analyzed. In order to meet the requirements, the polymer coater,filtrate reducer, thinner, shale-control agent for drilling fluid were optimally selected, and an organic positive gel_polymer drilling fluid was developed. The properties of the new drilling fluid system, such as inhibition, mud cake-forming capacity, filtrate control capacity, rheology, lubricity and formation protection ability were tested in laboratory. The functional mechanism of the drilling fluid was briefly investigated. The field test was made at CPS 185 Well. In the whole drilling, the wall of the hole was stable, and the hole diameter was regular. Electric logging, running casing and cementing operation were successful. Laboratory tests and in-situ application indicate that this kind of drilling fluid has the advantages of both positive gel and polymer drilling fluids, such as unique rheology, and excellent lubricity, inhibition, anti-sloughing,formation protection property and easiness for field maintenance and treatment.The successful application at CPS 185 Well demonstrates that the organic positive gel_polymer drilling fluid can meet the requirements for drilling horizontal side-tracked slimhole.