Fracturing method applicable to thin layer

Abstract

The invention provides a fracturing method applicable to a thin layer. The method comprises the steps that 1) comprehensive characteristic evaluation of a reservoir and a compartment is carried out to acquire the information of the lithology, the physical property, the rock mechanics, the crustal stress and the sensibility characteristic of the reservoir and the compartment; 2) at the acid liquid pretreatment phase, acid liquid is injected into the reservoir; 3) at the pre-liquid phase, low viscosity fracturing liquid is injected into the reservoir; 4) at the sand adding phase of sand-carrying liquid, a medium viscosity fracturing liquid system mixed with a propping agent is injected into the reservoir; 5) at the replacement phase, a less replacement technology is used. According to the invention, the fracturing degree of the reservoir of the class, the effective support degree of the propping agent and the support efficiency of a long shaft crack can be improved; the post-pressing long-term diversion ability is improved; the post-pressing effect is ensured; the stable yield period is prolonged; and the fracturing reforestation effect of the reservoir of the class and the reservoir utilization are improved.

Description

technical field [0001] The invention relates to the technical field of hydraulic fracturing of oil and gas reservoirs, in particular to a fracturing method suitable for thin layers. Background technique [0002] Thin layers are widely distributed in the Songliao Basin, Ordos Basin, Jianghan Basin and other regions in China, and have become the main successor blocks for tapping the potential and stabilizing production of old oilfields and increasing reserves and production in new areas. Fracturing is one of the most important means for increasing production of this type of reservoirs one. However, thin beds have the characteristics of thin reservoirs (thickness of a single sand layer is generally <6m), generally poor reservoir quality, strong heterogeneity, low natural productivity, and insufficient strength or thickness of upper and lower shielding layers. Fracturing has difficulties such as difficult control of fracture height, difficulty in "effective" support, poor lo...

AI Technical Summary

Problems solved by technology

[0004] 1. Unreasonable construction parameters make it difficult to control the fracture height, and it is difficult for the proppant to "effectively support": the fracturing construction displacement and construction scale are too large, resulting in excessive extension of the fracture in the longitudinal direction, but within the effective thickness range of the thin layer, "Effectively supported" fracture length and conductivity are seriously insufficient, resulting in rapid production decline after fracturing

[0005] 2. The support profile of proppant is unreasonable, and the "propping efficiency" of fractures in the far-well zone is low: the suspension performance of proppant at the fracture height in the far-well zone is poor. The proppant settles in the bottom interlayer; even in the effective thin layer range, the propping section of the proppant is unreasonable, so that the propped fracture near the wellbore can cover the entire effective thickness of the sand layer, while the propped fracture in the far wellbore zone covers the effective sand layer. The probability of the effective thickness of the layer is greatly reduced, which greatly reduces the "propping efficiency" of the fracture (the ratio of the proppant dose that plays a propping role in the thin layer to the total proppant dose that enters the well) is greatly reduced

In fact, there are mudstone interlayers in the upper and lower interlayers of the thin layer. In the area of ​​the fractures that the fracturing fluid passes through, due to the excessive extension of the fracture height, the area occupied by the fractures in the upper and lower mudstone interlayers is relatively large. The shale content of the formation is high, and the content of various water-sensitive minerals is higher than that of the reservoir, which is likely to cause mudstone hydration and large-area expansion and migration of clay; on the one hand, it affects the flowback of fracturing fluid, and on the other hand, the The hydrated mud cake and expansive minerals will migrate into the fractures of the reservoir, causing secondary blockage and seriously affecting the effective conductivity of fractures

[0007] 4. It is difficult to comprehensively balance and optimize the relationship between fracture height extension and proppant settlement: even if the fracture height is well controlled during fracturing, the fracture height is relatively low due to the small thickness of the thin layer. Due to the settlement of the proppant, the flow channel of the fracture will be quickly blocked, resulting in early sand plugging

[0008] Through the search of relevant literature and patent database, the current research on thin layer fracturing mainly focuses on the integration of various factors or the use of various methods to avoid or control the extension of fracture height, focusing on the control of fracture height in thin layer fracturing. However, there are relatively few research reports on the mechanism and overall implementation process of thin-layer fracturing, and a set of mature and systematic methods have not yet been formed.