Controlling Fracture Height in Fracturing Effect Prediction of Oil Well Based on Uncertain Multi-Attribute Decision Making

Abstract

Hydraulic fracture to oil well, creating fracture in the bottom stratum, making the crude oil flow to the bottom along the fracture are common stimulation treatment used in oil field. Controlling fracture height fracturing is controlling the extension of fracture within oil layer area, which is the key to success or failure of hydraulic fracturing. Especially, controlling fracture height to avoid pressing to wear the near water layer, which causes a sudden increase of oil water production, is particularly important to oil production. Fracture extension theory and field practice indicate that in controlling fracture height fracturing process, the fracture height extension is related with reservoir stress difference of oil layer and adjacent barrier on a certain scale of construction also it is related with the 8 parameters such as the rock Young's modulus, fracture toughness, Poisson's ratio, permeability, reservoir thickness, fracturing fluid viscosity and fluid loss coefficient and so on. This study introduces uncertain multi-attribute decision making method to the well needing controlling fracture height fracturing, takes expected minimum fracture height as the target, concentrates the 8 attribute values of oil well with OWA operator, obtains comprehensive attribute value, and sorts the expected oil well fracturing effect according to the size of comprehensive attribute value, then selects construction well according to the sort results. In this way, it not only solves the difficulty to accurately resolve fracture height of analytical method and problem of large calculation of numerical method, also provides a simple and practical method for live well selection. According to fracturing selection of Changqing oil field 5 wells and on-site application comparison of 2 wells, it is consistent with the prediction result.