Comparative Experimental Study of Fracture Conductivity of Carbonate Rocks under Different Stimulation Types

Abstract

Carbonates have great potential for development, but the use of propped hydraulic fracturing or acid fracturing stimulation types alone has limited effectiveness. This study collected four sets of rock samples from three carbonate reservoirs: dolomite, limy dolomite, and limestone. The laboratory analysis focuses on propped hydraulic fracturing, acid fracturing, and acid fracturing plus proppants of these rock types. The aim is to assess acid erosion, proppant embedment depth, and the impact of varying proppant sizes and acid injection on fracture conductivity. The results showed that acid fracturing substantially enhanced the hydraulic conductivity of the three rocks. The embedded depth of the small-sized proppant was greater, but the fracture conductivity of the large-sized proppant was greater. Under the conditions of the actual pressure of formation of 55.2 MPa in the target reservoir, using 70/140 mesh proppant, 20% thickened acid, and an injection rate of 20 mL/min: for the dolomite-type rock, the propped hydraulic fracturing method had the highest fracture conductivity, which reached 151.17 D·cm. For the limy dolomite-type rock, the acid fracturing plus proppant experiment had the highest fracture conductivity, which was 157.26 D·cm. For limestone-type rocks, acid fracturing had the highest fracture conductivity of 210.39 D·cm. This study helps to elucidate the mechanism of different stimulation types and provides useful guidance for the more effective development of carbonate oil and gas reservoirs.

Fracture Conductivity Prediction Based on Machine Learning

“…Hydraulic fracture quality is the core of hydraulic fracturing quality, and fracture conductivity is particularly important. − The prediction of fracture conductivity is not only the basis of fracture optimization design but also one of the key parameters to determine the effect of hydraulic fracturing. − At present, the main research method for fracture conductivity is based on indoor testing methods. Xiao et al took carbonate rock as the research object and experimentally studied the effects of acid erosion, proppant embedding depth, and different proppant sizes and acid injection on fracture conductivity during hydraulic fracturing and acid fracturing; Guo et al conducted tests on steel plates and shale to understand the effects of flowback rate, fracturing fluid, and closure stress on proppant flowback and fracture conductivity; Sun et al used ceramic and quartz sand proppant obtained from Changqing Oilfield in China. For example, the fracture conductivity under different proppant mixing ratios was evaluated through experiments; Tariq et al .…”