Research and Application on Nitrogen and Dissolver Assisted Horizontal Well Steam-injection to Develop Shallow Thin Super Heavy Oil Reservoirs

摘要

Chun-feng heavy oil field is located in Junggar Basin, western China. Dead oil viscosity is commonly more than 5×10~4mPa·s. The depth of the heavy oil play ranges from 400 to 500m underneath with net pay of 2 to 7m. Porosity is about 30% and permeability ranges from 5000 to 6000 md. Traditional development techniques such as steam-injection using vertical well are not effective due to tremendous heat losses, limited heat radius with thin netpay and low drainage energy. Chun-feng oil field is developed integrally and successfully by using N2 and Dissolver Assisted Horizontal well Steam-injection technology. Peak oil production rate is up to 32t/d, which is 3 times more than that of wells using traditional technologies, and oil-steam ratio is 0.47. In order to improve steam quality and enhance steam sweep efficiency, new techniques combing horizontal well assisted steam injection with N2 and dissolver are proposed to develop this kind of heavy oil reservoirs. Study also shows that high efficient dissolver may decrease the viscosity of the heavy oil around wellbore and increase injection steam quality; meanwhile, N2 assisted steam injection may increase the volume of injection steam, enhance the drainage energy, and decrease heat losses around wellbore effectively. By the means of plug injection of dissolver and N2 assisted by horizontal wells, super heavy oil may be recovered effectively. Techniques mentioned above are proved to be very effective for the development of shallow thin super heavy oil reservoirs. Moreover, it is of practical significance which has been proved by successfully applying those techniques to Chun-feng oil field with over 3000×104t proven oil reserve.