Effect of variable perforation configuration on proppant transport and distribution using slickwater, The

Abstract

Hydraulic fracturing stimulation has unleashed prolific production from unconventional reservoirs. Horizontal drilling is used in conjunction with multi-stage hydraulic fracturing to increase the recoverable reserves by increasing the reservoir contact area. The target formation is drilled horizontally and then several hydraulic fracturing stages are created starting from the toe stage to the heel stage. Injecting the fracturing fluid at a high injection rate creates the fractures and is followed by proppant-laden slurries to ensure the conductivity of the fractures. One of the main challenges in multi-stage, multi-cluster treatments is distributing the proppant evenly between the different perforation clusters. Uneven proppant distribution might impact the fracture conductivity and ultimately influence the well productivity. The main objective of this research is to experimentally study the effect of changing the perforation configurations on the proppant transport and distribution using fresh water. Additional objectives include investigating the effect of injection rates, proppant concentrations, and proppant size on the proppant transport and distribution between multiple perforation clusters. A final objective is to develop experimental correlations to predict the transport and distribution behavior of the proppant as a function of perforation configuration. The experimental setup consists of a 30-foot transparent horizontal wellbore with an internal diameter of 1.5 inches. The horizontal pipe has three perforation clusters separated equally by 6 feet. Each perforation has 4 shots per foot with 90o phasing combined with a valve to control the flow at each perforation. This helped to accomplish different perforation configurations by controlling each perforation individually. To simulate slickwater fluid used in the field, fresh water with no additives was used for all experimental tests as the carrier fluid. Experimental tests were conducted on 100-mesh brown sand and 40/70 mesh white sand using a wide range of proppant concentrations and injection rates. The experimental results indicate that the proppant transport and distribution is highly influenced by the perforation configuration. The 100-mesh sand shows an even distribution at a lower proppant concentration using a 1 SPF, top perforation configuration. However, higher concentrations of the 100-mesh sand were received at the toe cluster using higher proppant concentrations. On the other hand, 100-mesh sand exhibited a heel-biased uneven distribution using a 1 SPF, bottom perforation configuration at all tested parameters. The 100-mesh sand indicated even proppant distribution using 2 SPF at higher injection rates. Using 3 SPF and 4 SPF showed a toe-biased distribution at all tested parameters. The 40/70 mesh sand exhibited similar distribution behavior to the 100-mesh results most of the time. However, the 40/70 mesh sand behaved differently using the 1 SPF, top perforation configuration at low injection rate resulting in an even distribution. The 40/70 mesh sand distribution showed a heel-biased uneven distribution using 2 SPF at all tested parameters. The sand settling at the bottom of the horizontal wellbore is affected significantly by the injection rate and perforation configuration. The high momentum associated with the higher injection rates helps in suspending the sand particles to the toe clusters. The highest sand settling was observed using the 1 SPF, top perforation configuration at low injection rates, whereas the lowest sand settling found using 4 SPF at high injection rates. The sieve analysis of the 100-mesh and 40/70 mesh sands showed the capability of fresh water to transport coarser sand particles to the toe cluster at high injection rates. The obtained experimental results in this research were used to develop a novel experimental correlation using Buckingham’s pi-theorem to predict the proppant distribution between multiple perforation clusters. The developed correlation includes different independent variables such as the injection rate, proppant concentration, proppant size, pipe diameter, and number of perforations. Comparing the actual experimental values to the developed correlation shows low error values of 5 to 11% for most of the tested configurations on the 100-mesh sand.