Study And Application Of Fluid Loss Controller For Oil Well Cement

Based on the analysis of physical and chemical property of NVP, one kind of oil well cement fluid loss controller with main component of AM/AMPS/NVP tri-copolymer was synthesized. Its structure was characterized by infrared ray and its properties of anti-high temperature and anti-salt were investigated. After adding it into oil well cement, its performance was evaluated, based on free water, rheological parameter, fluid loss, compressive strength, atmospheric thickening time, booster thickening time test. At the beginning of the test, initiating agent was selected and orthogonal test- for free radical polymerization was performed by four factors and three levels. Aiming at investigating fluid loss, the effects of reaction time, reaction temperature, monomer ratio, solution dosage on polymerization technique were compared. The best synthesized time was confirmed by adjusting the dosage of initiating agent. The additive has good capability of anti-high temperature and anti-salt due to its molecular structure. As the main component, blended with other material, it can control fluid loss of cement slurry, even cement slurry prepared with salt. With the dosage of 3%, , its API fluid loss was below 50ml at 95℃and 6.9Mpa. The fluid loss controller is an anti-high temperature and anti-salt copolymer and has excellent thermal stability due to lead of sulfonic acid group and pyrrolidone link. When salt concentration was up to 18%, API fluid loss was still below 50ml. This copolymer can retard setting effectively and regulate thickening time used with early strength agent. At high temperature, AM/AMPS/NVP polymer is absorbed on the surface of cement particles, so that cement hydration can not be retarded and the cement sets in a short time. After mixed with high temperature retarder, the high temperature retarder is absorbed on the surface of cement-hydrate, preventing cement particles contacting with water to retard cement setting. It can be used with some other additives like high temperature retarder at 200℃or above. Test results show that it is resistant to high temperature and salt, with low fluid loss and no free water, and has no detrimental effect on cement property such as rheology, compressive strength, etc. Shengke-1 Well, a key exploratory well of SINOPEC, is the deepest in the developing history of Shengli Oil Field, with total depth of 7026m, barefoot isolation section depth of 2873m, up to 150℃on top and 251℃at bottom. Salt-gypsum bed was encountered while drilling at bottom. Through various tests on properties and compatibility, this fluid loss controller is successfully applied to Shengke-1 Well, Fengshen Block, achieving good efficiency.