The Research Of Resistant High Temperature Water Shutoff Agent

The resistant high temperature water shutoff agent in the Daqing Oilfield hasnot been developed yet. In order to solve water plugging and channeling problemsthat occurred in the deep wells in the Daqing periphery-oilfield and other oilfields,and to provide one kind of reliable plugging technique, 120 ℃ resistant hightemperature water shutoff agent was proposed and developed.The main ingredient,modified Polyurethane Qingning, and the feasible additives can control the reactionspeed, self-solidification time, reactant intensity, thus meets the needs to plug thewater intervals and channeling in the deep wells.The beginnings and ends in the chain of Polyurethane Qingning are livelyisocyanogen acid (-N=C=O). After adding the catalyst and pushing the water shutoffagent into the formation, the isocyanogen acid groups react with water very quicklyunder the formation temperature and the pressure. The molecular linkage willexpand the chain, release the gas, branch the chain and crosslink the chain, whichcontribute to forming the dissolving solid in the hole to plug the water shutoff andchanneling passage.The reaction process, the reaction mechanism and the response type of 120 ℃high temperature agent are basically similar with those of 50 ℃, 70 ℃, 90 ℃ agentswhen they react with water. But as a result of synthesis formula change, resultant'sstructure and performances also change.The chains of Qingning precondensates are composed of the rigid segment andthe flexible segment. When changing the flexible segment --hydroxyl polyether'stype and its molecular weight, and rigid segment --aromatic isocyanic acid ester'stype and function, solid's intensity, the heat resistance, the compressive strength andother performance will also vary. Moreover, when changing the equivalence ratio ofisocyanic acid ester and hydrogen class compound, solid's performances also changealong with it.During the research of resistant high temperature modified water shutoff agent,we have mainly done the following three aspects work for Qingning agent to resisthigh temperature.First, after joining polyether polyols N2, the N2 molecular weight and functionbecome quite different from N1. Thus the groups with high inner energy, mainly-NH-CO-NH-(ureido-Dcarbamido) and -NH-COO-(amino formyloxy), in the finalresultant can rise. That is the main reason that modified agent can resist hightemperture and increase the compressive strength.Second, through introducing isocyanogen ester T1, the ratio of the isocyanogenester and the reactive hydrogen class compound (-NCO/ -OH) in the raw material ischanged, Crosslinking's density will also vary.Third, appropriate crosslinking agent D was screened out, which can enhancethe final resultant's crosslinking density, the compressive strength, and increase theheat resistance and the bearing strength.The modified agent features fast reaction speed, good veering performance,high bearing strength, long validity, and easy unplugging. It can resist 120 ℃. Theweak acid and the alkali have no influence to its resultant. The reaction time isbetween 10 seconds to 30 seconds;the gelatin time is within 2 minutes;theself-solidification time is within 15 hours;the resultant can bear 20Mpa pressuredifference;and the agent's restore time is over 3 years. All of these parameters canguarantee the need to plug the watered-out layers and channeling intervals in thedeep wells.This project was tested by the field operation from March 2004. 2 wells wereplugged by using the 70 ℃ modified agents. One well is a channeling well,GX109-6 Well in the Jidong oilfield;the other well is watered out well, La Two inthe periphery of Daqing oilfield. After plugging the watered-out layers and thechanneling intervals, both two wells have good effect.