【作者】 张锋；

【导师】 程远方；

【作者基本信息】 中国石油大学 ， 油气工程力学， 2009， 博士

【摘要】 我国是一个低渗油气藏资源比较丰富的国家,未动用的油气地质储量中,低渗油气藏占的比例很大。目前低渗透油藏主要采取注水开发,但由于低渗透油藏特殊的孔隙结构以及注水伤害等原因,导致注水困难,波及系数降低,采收率减小。目前增强注水主要有物理方法与化学方法,主要包括常规压裂增注、振荡、酸化等增注技术,但均存在有效期短、费用较高、二次伤害等问题。裂缝扩展注水技术是运用常规的水力压裂原理,在低渗透油藏注水井中实施的一种提高注水量的技术措施。低渗透油藏中,由于储层的渗透率较低、渗流阻力大、以及常规注入水水质的影响,使地层吸水能力差。在这种情况下,保持注水量不变,提高地面注水压力,当井底压力达到地层破裂压力时,就会在沿垂直于最小主应力方向产生裂缝。缝表面未受污染,吸水能力增强,此时若仍保持注水量不变,地面注水压力瞬间会自然下降到某一值。继续注水,由于水质、出砂等原因污染新裂缝表面,注水压力逐渐上升,当达到地层破裂压力时,在裂缝尖端,又会沿原裂缝方向产生新的裂缝,新缝表面渗透率增加,注水压力瞬间降低。以此类推,裂缝扩展呈现不规则的周期变化,缝长逐渐增加,直至合理的范围。论文以岩石力学和渗流力学为基础,对裂缝扩展注水技术的内在机理进行了系统研究。首先,研究了裂缝扩展注水的机理,形成了裂缝扩展注水的力学模型,建立了裂缝扩展周期、滤失系数以及裂缝扩展缝长增量的计算方法;其次,采用双向通信方法,把裂缝生长模拟与油藏模拟进行整合,形成了裂缝扩展注水动态模拟软件,并进行了裂缝扩展注水开发影响因素的规律性分析。最后以胜坨油田为工程背景,开展了裂缝扩展注水技术参数的优化设计。得到如下结论:对于低渗透油田,裂缝扩展注水技术对采收率的影响显著;对采收率有影响规律:0°裂缝的采出程度略低于理想状态下的采出程度,而45°和90°裂缝采出程度与理想注水采出程度一致;且裂缝扩展注水的采出程度远高于无压裂常规注水的采出程度。0°裂缝时波及系数最大,45°裂缝时次之,90°裂缝时更小,理想状态无裂缝时波及系数最小。注入量对裂缝扩展开发效果有影响:在本研究所用参数条件下,注入量为60方/天时,0°裂缝和无裂缝理想状态下采出程度基本一致,注入量80方/天时,有裂缝与无裂缝状态相比,采出程度有所降低;注入量100方/天时,采出程度降低幅度有所增大。水质对裂缝扩展注水的影响规律:无论水质好坏,90°和45°裂缝扩展对采出程度影响很小;0°裂缝时,水质好采出程度高,但影响幅度不大。水质对波及效率的影响很小。井距对裂缝扩展注水的影响规律是:随着井距的增加,任意角度裂缝的采出程度都在下降。井网类型对裂缝扩展注水的影响规律是:裂缝扩展注水与不压裂理想注水的规律一致,即反九点法的采出程度略有降低,其它井网相同。注水时机的影响规律是:越早注水,采出程度越高。但最终采收率相差并不是非常大。不论何种情况,与考虑注入量下降情况相比,裂缝扩展注水技术能够大程度提高采出程度,有着广阔的应用前景。更多还原

【Abstract】 Low-permeability reservoirs are rich in China. The low-permeability reservoirs account for a large proportion in the unused oil and gas geological reserves. At present, low permeability reservoir development is mainly depend on water flooding, but the special pore structure and water damage lead to difficult in injecting water, this reduce the sweep efficiency and recovery. There are two main ways which physical methods and chemical methods to enhanced water, mainly including conventional fracture, oscillation and acid etc to increase injection flow rate, but there are short valid, higher cost and secondary damage and so on.Fraction Propagation injection technology is proposed as a new measure which apply the principle of conventional hydraulic fracturing to increase injection water in low permeability reservoir, because the low permeability and high flow resistance, as well as the conventional into the impact of water quality, this lead to bad absorbing capacity. Under such circumstances, maintaining constant injection of water, improving the ground water pressure, when the stress reached the formation fracture pressure, there will be along the perpendicular to the direction of minimum principal stress fractures. Fracture surface were not contaminated, water-absorbent capacity enhance, and the ground injection water pressure will be instant down to in value. If the injection of water remains unchanged at this time. Pressure will be increase because of water on quality, sand production etc factors pollute the new sand surface of fractures during continue injection water process, a gradual increase in water stress, when the formation fracture pressure reached breakdown pressure, in the tip along the original fracture direction will generate a new fractures, new fractures surface permeability increased, water injection pressure reduce down instantly. And so on, fracture propagation appears an irregular cycle, fracture length increase until the scope of reasonable.In this paper, based on rock mechanics and fluid mechanics in porous medium,system study on fracture propagation mechanism. Firstly, the mechanism of fracture propagation mechanism is studied and developed mechanical model, building fracture propagation cycle, filtration coefficient and incremental long of fracture propagation Secondly, the fracture growth simulation and reservoir simulation is integrated to form a fracture propagation injection dynamic simulation software through two-way communication method, and the affecting factors of fracture propagation injection development is analyzed. Finally taking Sheng tuo Oilfield as example, parameters of fracture propagation injection technology are designed and optimized. Get the following conclusions:For low-permeability oil fields, it is remarkable for fracture propagation injection technology to enhance recovery , fracture affect the direction of fracture propagation effect :zero degree fracture recovery was slightly lower than the ideal state of degree of recovery, however recovery of forty-five degree and ninety degree fractures in according with the ideal state; and degree of reserve recovery of fracture propagation injection is much higher than conventional fracture sweep efficiency . sweep efficiency of zero degree fracture is the largest ,forty-five degree fracture take second place, ninety degree fracture less that , and without fracturing is the smallest at the ideal state.The effect of Injection volume on fracture propagation: the parameters used in the study, oil zero degree fracture is according with ideal state in recovery when the rate of injection of sixty square every day, injection volume of eighty square every day, the recovery of fractures compared with no fracture status is reduced; when injection volume of one hundred square every day, the recovery of decrease appear increased.The effects of water quality on fracture propagation: the effect of ninety degree and forty-five fracture propagation on recovery is negligible whether water quality is bad or good, fractures, recovery is high with the better quality when zero fracture but the affect is small. Water quality has little affected on the sweep efficiencyThe effects of well spacing on fracture propagation: the recovery is on the decline at any angle fractures in with well spacing increasing. The effects of well pattern on fracture propagation: fracture propagation injection is consistent with the ideal water injection with no fracture. That is, inverted nine spot flooding pattern slightly reduce the degree of recovery, other pattern is same. The effects of timing of water injection on fracture propagation: the earlier in the injection, the higher in recovery. However, the difference of ultimate recovery is not very great. No matter what circumstances, fracture injection technology can improve recovery at a large extent compared to taking into injection rate decline and have broad application prospects.更多还原