Study On Technology Of Cementing Anti-gas Channeling In Gas Well Of Liaohe Oilfield

The viscosity of natural gas is much lower than that of water or oil, and gas has a fastervelocity through microannulus between cement stone and annulus interface to wellhead,leading to much easier gas channeling in natural gas wells. The cementing merit rate is just50%in Da Mingdun concavity of Shenyang oil factory and Niu Ju Structure of Ci Yutuo oilfactory in Liaohe Oilfield. One of main reasons causing low merit rate is annulur channeling.So the anti-gas channeling technology is studied in natural gas well of Liaohe Oilfield.In order to improve displacement efficiency, centralizer intervals were designed andproperties of flushing fluid and spacing fluid were optimized. The influences of eccentricity,casing size and surface condition on bond strength and permeability of cement paste werestudied. Based on relationship between static characteristic and dynamic characteristic ofcement slurry, the anti-gas channeling performance was predicted. After optimization ofdynamic parameter measurement method, anti-gas performance prediction method wasimproved. Analyzing influence of additives on cement slurry properties, anti-gas channelingcement slurry was developed. New well enlargement instrument overcame its shortcomingand was used field experiment. At last, a series of natural gas well cementing technologieswere formed.The space of centralizers were calculated according to the deformation relations of thevertical and horizontal bending, uniform load twisted supported beam. After cleanup in5min,the bond strength is close to that there is on mud attached to the annulus. The largest bondstrength can be got when sand grains in20mesh size are attached on the annulus. To get goodsealing performance, eccentricity must be lower than30%. The anti-gas channelingperformance can be accurately predicted using the thickening time difference which decreasesas rotate speed increases. Thickening time measured in the speed of higher or lower than150rpm (API standard), can shorten100min or prolong60min. The simulation rotate speedmeasuring thickening time of cement should be determined according to the displacementvelocity and rheological parameters. QA plasticizer can improve cement paste plasticity, fluidloss additive LT-1, early strength agent SW-3and dispersant SXY have good compatibility with QA plasticizer. The anti-gas channeling cement slurry developed can be used in naturalgas cementation. The strength and abrasion resistance of cutting tips of well enlargementinstrument can be raised by use of polycrystalline diamond. Extension tool improves thestability and swallow tail sulciform anti-fallout equipment enhances the safety. The fieldexperiments have significant effect.