Research On The Sanding Prediction In Horizontal Wells With Multi-thermal Fluids Injected And Produced

As we know, the heavy oil reservoir of China is abundant and widely distributed. However, sanding is an inevitable problem during the production of this oil reservoir, especially in the later period of the well with high-frequent multi-thermal fluids injected and produced. The factors which influence the sanding of offshore oil wells with multi-thermal fluids injected and produced are numerous and complex. So with the help of accurate prediction and effective prevention, we can make these wells long-lived and obtain greater economic benefits.In order to solve the problem of sanding in offshore oil wells with multi-thermal fluids injected and produced, considering the structure of these wells and the characteristic of multi-thermal fluids, with the help of Thermodynamics and pressure field model, we built the temperature and pressure distribution model of wellbore and formation, which applies to the whole stage of heat injection. On this basis, we got the dynamic sand production prediction of wells with multi-thermal fluids injected and produced, researched the change regulation of thermal stress of reservoir, crustal stress and rock strength which influenced by sand production, rising of water contain, decreasing of reservoir pressure, and changing temperature of fluids injected. According to the forecast model about critical condition of sanding, we predicted the critical pressure drawdown and production of thermal reservoir. This paper analyzed how the start-stop of boiler and intermittent pumping of gas-liquid influence the pressure and temperature, and then how they affect sanding.According to the model above, we developed software to predict sanding of horizontal wells with heat fluids injected and produced, and applied it to typical offshore wells of Bohai oilfield. The conclusion is: with the heat injection, the reservoir temperature rises, the critical pressure drawdown turns from 1.92 MPa to 1.25 MPa, and the risk of sanding increases; During oil well’s production, the critical press drawdown returns up to 1.4MPa, while the temperature decreases; That is, sand production will most likely to occur in the beginning of heat fluids produced. By analyzing the sensitivity of heat injected reservoir’s pressure drawdown, we can obtain that it increases with the increment of Poisson ratio, internal cohesion and reservoir pressure; While decreases with the increment of reservoir temperature, water content and water saturation. During the heat injection, the average pressure of reservoir increases to peak value and then falls sharply, 360 days later, the pressure turns from 22.8MPa to 5.2MPa; the average temperature of reservoir can reach 160℃, and 360 days later, it will reduce to 65℃, because of its diffusion. The start-stop of boiler produces instantaneous high voltage around faucets, which has little impact on the reservoir In the distance. Similarly, the intermittent pumping of gas-liquid causes fundamental change about pressure in the shallow part of wellbore, with little impact on the deep. The research finding has guiding significance to predict sand production of horizontal offshore wells produced heavy oil, moreover, it lays a foundation for the follow-up study.