Proppant transport in horizontal wellbores has received significant industry focus over the past decade. One of the most challenging tasks in the hydraulic fracturing of a horizontal well is to predict the proppant concentration that enters each perforation cluster within the same stage. The main objective of this research is to investigate the effect of different perforation configurations on proppant transport, settling, and distribution across different perforation clusters in multistage horizontal wells. To simulate a fracturing stage in a horizontal wellbore, a laboratory-based 30-ft horizontal clear apparatus with three perforation clusters is used. Fresh water (~1 cp) is used as the carrier fluid to transport the proppant. This research incorporates the effect of testing three different injection rates each at four different proppant concentrations on proppant transport. Different perforation configurations are also used to test the perforation effect on proppant transport using similar injection rates and proppant concentrations for the tested 100-mesh proppant. The proppant is mixed with fresh water in a 200-gallon tank for at least 10 minutes to ensure the consistency of the slurry mixture. The mixture is then injected into the transparent horizontal wellbore through a slurry pump. This laboratory apparatus also includes a variable frequency drive, a flowmeter, and two pressure transducers located right before the first two perforation clusters. Sieve analysis is conducted to understand the ability of fresh water to carry bigger particles of the mixture at different injection rates, proppant concentrations, and perforation configurations.
The results show different fluid and proppant distributions occur when altering the perforation configurations, injection rates, and proppant concentrations. The effect of gravity is extreme when using a limited-entry configuration at each cluster [1 shots/ft (SPF)] located at the bottom of the pipe, especially at low injection rates, resulting in uneven proppant distribution with a heal-biased distribution. However, even proppant distribution is observed by changing the limited entry perforation configuration to the top of the horizontal pipe at similar injection rates and low proppant concentration. Increasing the proppant concentration reduces the void spaces between the particles and pushes them away toward the toe cluster. Even proppant distribution is also observed across the three perforation clusters when using higher flow rates and a 2 SPF perforation configuration located at both the top and the bottom of the pipe. The results show uneven fluid and proppant distributions between clusters with a toe-biased distribution when altering the perforation configurations to 3 and 4 SPF.
The results of the sieve analyses show different size distributions of the settled and exited proppant through different perforations and clusters. This illustrates the ability of fresh water to transport different percentages of various proppant sizes to different perforations and clusters within a single stage. Frequently, the injected proppant is assumed to be distributed evenly across the perforation clusters and the distribution of fluid and proppant is assumed to be identical. This research provides a better understanding of the proppant transport inside the multiclusters in a horizontal wellbore by using fresh water as the carrier fluid. This research is unique in that it experimentally studies the effect of changing the perforation configurations and orientation on the proppant transport and distribution. This study comprehensively investigates the effect of injection parameters that influence the proppant transport behavior such as injection rate and proppant concentrations. The work shows that the distribution of the transported proppant is different across individual clusters and varies between different perforations within each cluster. Such information is beneficial to understanding transport in horizontal, multistage completions and how such impacts the overall treatment efficiency, especially when employing limited-entry perforation techniques.