Abstract
A large amount of fracturing fluid will be injected into the unconventional reservoirs during hydraulic fracturing. At present, the maximum amount of fracturing fluid injected into shale oil reaches 70000 m3 in Jimsar. The main function of fracturing fluid is to make fractures for traditional reconstruction of fracturing; for unconventional reservoirs, fracturing fluid is also used to increase formation energy by large-scale injection. It is of great significance to improve the utilization efficiency of large-scale hydraulic fracturing fluid for shale oil to increase production and recovery. In this study, the method of improving the utilization efficiency of the large-scale hydraulic fracturing fluids is explored by experiment, numerical simulation, and field test of Jimsar shale oil formation. This research shows that fracture complexity can effectively increase the contact area between the fracturing fluids and the formation. The water absorption rate of the fractured core is increased, which lays the foundation for improving the liquid utilization efficiency. Reasonably, well shutting before production ensures the pressure balance in the fractures, and the fluid pressure can be transmitted to the far end, which improves the fracture effectiveness, increases formation energy, and promotes imbibition and oil displacement. By using the additive of enhanced imbibition displacement, the displacement efficiency and the displacement amount of crude oil in the micro-nanopores can be greatly improved, and the utilization ratio of liquid can be further enhanced. The experiment adopted in the field proves that improving energy utilization efficiency has an important impact on production. This study has great guiding significance for the efficient development and practical production of unconventional reservoirs.
Highlights
Unconventional resource exploitation requires higher technologies [1, 2]
In order to discuss the above problem, this study selects the bottom hole core of Jimsar Lucaogou formation and Yanchang formation of Ordos Basin to carry out the imbibition experiments, establishes the double medium numerical simulation model, analyses the field test of Jimsar shale oil, puts forward the concept of fracturing fluid utilization efficiency, and explores the method of improving fracturing fluid utilization efficiency from the action of fracturing fluid
Large-scale hydraulic fracturing brings a large amount of fracturing fluid and energy into the reservoir
Summary
Unconventional resource exploitation requires higher technologies [1, 2]. The permeability of the unconventional reservoir is usually less than 0.1 mD, and porosity is less than 10%; reservoir physical properties are poor. A large number of high-pressure fracturing fluids are injected into the reservoir to make the formation rock rupture, produce multilevel fractures and even connect the natural fractures, providing channels for the flow of oil and gas, greatly improve the seepage capacity of the reservoir, and increase the contact area between the reservoir and the wellbore [11, 12]. Unconventional oil and gas reservoirs usually have poor seepage capability, resulting in a small swept range of injected fracturing fluid and a small production range of the reservoir. The formation energy enhancement effect is not significant This makes the small pores with high capillary force unable to carry out imbibition and oil displacement and unable to increase production. In order to discuss the above problem, this study selects the bottom hole core of Jimsar Lucaogou formation and Yanchang formation of Ordos Basin to carry out the imbibition experiments, establishes the double medium numerical simulation model, analyses the field test of Jimsar shale oil, puts forward the concept of fracturing fluid utilization efficiency, and explores the method of improving fracturing fluid utilization efficiency from the action of fracturing fluid
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