氮气及降粘剂辅助水平井热采开发浅薄层超稠油油藏

Study and application on HDNS technology to develop shallow and thin super heavy oil reservoirs

准噶尔盆地西缘春风油田的超稠油油藏具有埋藏浅、粘度高、厚度薄的特点,常规直井注蒸汽开发效果差。根据油藏开发难点,提出了氮气及降粘剂辅助水平井热采(HDNS)强化开发技术,揭示了各要素的作用机理,即水平井降低注汽压力、增强吸汽能力、减少热损失;降粘剂有效降低井筒周围的原油粘度,提高注汽质量;氮气提高浅层油藏能量,具有助排、隔热作用,提高开发效果;蒸汽具有加热降粘和蒸馏作用。在春风油田排601超稠油油藏投产水平井54口,通过运用HDNS强化采油技术,第1a平均单井产油能力为8.2t/d,累积油汽比为0.48t/t,平均单井峰值产油量为32t/d,实现了浅薄层超稠油的高效开发。

Chunfeng heavy oil field is located in Junggar basin,western China.Ground degassing viscosity is commonly higher than 5xl04 mPa.s The depth of the heavy oil play ranges from 400 to 500 m underneath with 2-6 m of net pay.Porosity is about 30% and permeability ranges from 5 000x10-3 to 6 000x10-3 um2.Traditional development techniques such as steam-injection using vertical well are not effective due to tremendous heat losses,limited heat radius within thin layers and low drainage energy.In this study,it shows that super heavy oil is non-Darcy flow in porous media.In order to improve steam quality and enhance steam sweep efficiency,new techniques combing horizontal well assisted steam injection with N2 and solvent are proposed to develop this kind of heavy oil reservoirs.Study also shows that high efficient solvent 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 and make steam reach overburden effectively.By means of plug injection of solvent and N2 assisted by horizontal wells,super heavy oil may be recovered effectively.Moreover,well patterns,the extendibility of horizontal well steam flooding and economic-technique limits are studied.Based on the research,related thermal chemical techniques are successfully developed.Those techniques are proved to be very effective for the development of shallow and thin super heavy oil reservoirs.