Study And Application Of Profile Control With Gel In GGY Oilfield

Because of the global economy increases,the crude oil demand has continuously increased recently.Meanwhile,many oilfields cannot produce or produce hardly by natural energy due to their maturity status.So Water flooding become the most popular method used to sustain the reservoir energy.GGY oilfield is a typical low-permeability fractured reservoir,which faces two main kinds of problems during water flooding:heterogeneity of the reservoir and water channeling problem.The reservoir heterogeneity results in the water channeling problem,then in high water-cut and low oil recovery.To solve the water channeling problem,increase the oil recovery and reduce the water-cut,a kind of gel profile control technique has been carried out.This research has been conducted by indoor experiments and then applied in GGY oilfield,Erdos Basin,North Shaanxi,P.R China.A specific polyacrylamide/chromium gel was synthesized especially for GGY oilfield.The main chemicals used for this research are polyacrylamide polymer provided by Sinopharm reagent Company Ltd,with a molecular weight of 14 million,a hydrolysis degree of 25%and a solid content of 90%.A Chromium compound called XT-5 was used as the crosslinking agent,and thiourea provided by Sinopharm was used as the delaying agent.The viscosity and shear measurement were carried out by using a Brookfield viscometer,reprogrammable rheometer.A series of experiments,such as crosslinker selection,crosslinker concentration optimization,polymer concentration optimization,suitable p H value evaluation,and delaying agent concentration optimization was carried out.Then gel thermal stability under reservoir temperature(35 ~oC for 120 days),and shear stability of the gel(under a shear rate of 170/s)were investigated.Also,experiments on gel injection parameters such as injected gel volume,gel injection rate,gel injection mode,gel injected slug position were carried out,and then the impact of permeability on the gel plugging ability was evaluated.Lastly,we applied this technology in GGY oilfield with the optimized gel formula.The appropriate gel formula was obtained with a polymer concentration of 3000 mg/L-4000 mg/L,a crosslinker concentration of 50 mg/L and with a crosslinker-delaying agent ratio of 1:0.6.The optimized gel showed excellent thermal stability under reservoir conditions(35~oC)for four months and excellent shear stability under 170/s.The indoor test results showed that the maximum recovery rate was obtained with the middle position of the slug in the sand pack,an injected volume of 0.3 PV.The efficiency of the measurement showed as following,the daily production of production wells has increased by 140%;water content decreased by35%;and the cumulative incremental oil production had reached 457.83 tons in six(6)months,showing good applicability of these techniques in GGY oilfield.