The Comb-shaped Polymer Profile Control Performance Evaluation

This paper aiming at the situation of the heavy profile control workload for Henan Oilfield water flooding blocks and the existing polymer’s large dosage, high cost and poor performance, the polymer profile control performance evaluation was carried out. Multilevel full experiment method was used and the comb-shaped polymer KY-6was made comparison with the polymer1630and Zhengli Ⅱ.Low temperature experiments and high temperature experiments were included in all Experiments. For the low temperature experiments, polymer’s cross-linking situation was researched in Shuanghe injection water and polymer injection spitting water with three different concentration(0.1%、0.2%、0.3%), adding chromium cross-linking agent with three different concentration(0.1%、0.2%、0.3%), in the condition of50℃,60℃、70℃. For the high temperature experiments, polymer’s cross-linking situation was researched in Shuanghe injection water、Jianghe injection water、Zhaowa injection water、polymer injection spitting water and the20000mg/L simulative formation water with three different concentration(Shuanghe、Jianghe、polymer injection spitting water and simulative formation water for0.1%、0.2%、0.3%, Zhaowa for0.1%、0.15%、0.225%),adding aldehyde cross-linking agent with three different concentration (Shuanghe、Jianghe、polymer injection spitting water and simulative formation water for1%、2%、3%, Zhaowa for1%、1.5%、2%), in the condition of80℃、90℃、100℃、110℃. Through the experiments, the gel performance of different polymer cross-linking systems was studied; the influence of polymer concentration、cross-linking agent concentration、temperature、salinity Polymer/Cross-linking agent ratio and polymer injection spitting water to gel performance was also researched; and the long-term stability of different polymer cross-linking systems was assessed. Comparing to the gelling effect of the three kinds of polymer cross-linking systems, profile control system formulas which were suitable for three blocks were given preferentially. They are0.1%1630+1%chromium cross-linking agent for Shuanghe low temperature area,0.2%KY-6+1%aldehyde cross-linking agent for Shuanghe high temperature area,0.2%KY-6+2%aldehyde cross-linking agent for Jianghe area,0.15%KY-6+1.5%aldehyde cross-linking agent for Zhaowa area. The storage modulus G’and loss modulus G" of these formulas were tested. The result that all the G’values are greater than10Pa shows these formulas are strong gel.A mount of indoor evaluation experiments and the core physical model gel experiments showed that:(1)Under the high temperature and salinity conditions, the gelling situation of KY-6is better than1630and ZhengliⅡ, whose every system could crosslink without degradation, showing good temperature tolerance, salt resistance and stability. What’s more, the gelling situation of the comb-shaped polymer is similar with1630and ZhengliⅡ with only two-thirds usage.(2)The gelling speed was too fast with1%chromium cross-linking agent, so the use concentration should be reduced. The gelling time of polymer cross-linking system is obviously extended with0.2%chromium cross-linking agent. Aldehyde cross-linking agent fits well with the low temperature reservoir.(3)With100℃, Zhaowa injection water, the aldehyde cross-linking agent concentration is1.5%,and KY-6concentration is respectively0.1%,0.15%, and0.225%,thus the viscosity of these systems is14338mPa-s、19196mPa-s and20349mPa-s, which means, with a certain cross-linking agent concentration, the higher the polymer concentration,the greater the gel viscosity;with90℃, the KY-6concentration is0.15%,and the aldehyde cross-linking agent concentration is respectively1%、1.5%、2%,thus the viscosity of these systems is17217mPa-s、19736mPa-s and21200mPa-s,that’s to say, with a certain polymer concentration, the greater the cross-linking agent concentration,the greater the gel viscosity.(4)The temperatures of0.15%KY-6+1.5%aldehyde cross-linking agent system are respectively80℃、90℃、100℃、110℃in the Zhaowa injection water, and the viscosity of the system is respectively17762mPa-s、19736mPa-s、19196mPa-s、17276mPa-s,namely,the higher the temperature is, the greater the gel viscosity is. But it goes down to the contrary, when temperature is beyond a certain temperature range.The perfect temperature is around90℃.(5)The gel viscosity of0.2%KY-6+2%aldehyde cross-linking agent system in the pure water is9236mPa-s, the gel viscosity is respectively22780mPa·s、19872mPa-s、14293mPa-s、14050mPa-s in Zhaowa、 Shuanghe、Jianghe injection water and the20000mg/L simulative formation water. It shows that the gel viscosity with certain mineralization is greater than pure water system,namely, certain mineralization is good for the generation of gel; The water salinity in rising order is Zhaowa injection water、Shuanghe injection wate、Jianghe injection water, and simulative formation water,that’s to say, as the increasing of the system salinity,the gel viscosity decreases.(6)Decreasing the polymer concentration and cross-linking agent concentration will extend the gelling time and viscosity of polymer cross-linking system when the concentration of polymer and cross-inking agent reduces to a certain degree (Polymer/Cross-linking agent ratio for500/5000), only comb-shaped polymer can crosslink in Zhaowa injection water, which are not under other conditions.(7)The system of0.07%Zhengli Ⅱ+1%aldehyde cross-linking agent can crosslink under100℃in Jianghe、Zhaowa and Shuanghe injection water. But the0.05%ZhengliⅡ+1%aldehyde cross-linking agent system can not crosslink under100℃in the above three kinds of water. While the system of0.05%Zhengli II+1%aldehyde cross-linking agent can crosslink under100℃in polymer injection spitting water. It’s Initially determined that polymer injection spitting water at least contains200mg/L polymer.(8) The long-term stability of different polymer cross-linking systems has been evaluated.After90days, the viscosity retention rate of the system of0.15%polymer+1.5%cross-linking agent is followed by:KY-6:53%,1630:21%,ZhengliⅡ:27%; the viscosity retention rate of the system of0.2%polymey+1%cross-linking agent is followed by:KY-6:72%,1630:38%,Zhengli II:42%; the stability of comb-shaped polymer is better than1630and Zhengli II.(9)The formed gel of the formulas makes blocking rate be above95%in the core. The retention rate of blocking rate is above99%through the30PV water scouring. The blocking rate and erosion tolerance ability are both good.(10) Sand packed tube model experiments showed that under the combination method:every block formula with injection pore volume multiple for0.3PV, lead slug+subject slug+rear slug, improving the extent of oil recovery is up to the highest, reaching up to above15%. Parallel cores improving the injection profile showed that the injection profile of parallel core gets some certain improvement after profile control. The improvement rate of injection profile is up to above85%. The EOR of high permeability formation reaches up to above12%, The EOR of low permeability formation is above17%.(11) Take Zhaowa area for instance, the formula of different polymer cross-linking systems with injection pore volume multiple for0.3PV, the extent of EOR of KY-6,1630and Zhengli Ⅱ is respectively:15.49%,14.26%,14.38%, while the formula prices of KY-6,1630and Zhengli Ⅱ as raw materials are followed by:119.8RMB,133.47RMB,132.55RMB. So, when injecting the profile control agents at the equal pore volume multiple, the formula of comb-shaped polymer KY-6as raw material makes the extent of EOR up to the largest. And the price of profile control agent each ton is the lowest. The economic benefit is remarkable.