Within the last decade, technical advancements in horizontal drilling have created an environment in the hydraulic fracturing industry resulting in a paradigm shift for the completion of unconventional wells. This shift away from conventional, vertical, bi-wing fractures with large diameter proppant, to the current unconventional design of multi-zone laterals, requires a new generation of proppants and carrying fluids. This proposes a challenge to the industry to successfully place proppant into the far field regions of potentially multiple fracture networks. To meet this challenge the industry has dedicated numerous resources to study proppant transport behavior and carrying agent behavior to better understand and apply materials that will economically optimize well completions.

This paper focuses on how proppant is transported with different fracturing fluids using a combination of pipe flow and patent-pending slot flow tests to study their behavior in various sections of a simulated fracture, including near-wellbore and far-field (low shear) fracture environments.

The objectives for the project are defined as:

  • Identify proppant transport characteristics (40/70 and 100 mesh frac sand) through an open channel of high shear, low shear, leak off and low-to-zero shear environments with various fluids (slickwater, HVFR, linear gel and crosslinked gel).

  • Determine how changes in geometry (incline, decline, dead-end, drop-off, and banking) impact proppant placement.

  • Determine the carrying capabilities of various fluids with 40/70 and 100 mesh proppants.

Comprehensive testing was performed on three separate test designs: pipe flow, standard 4′x8′ slot flow and patent-pending 4′×8′ slot flow with obstructions inside the structure. Test procedures are designed to simulate a typical West Texas unconventional well with 100 bbl/min, 5 ½″ casing, 15,000′ of casing. Fluids are conditioned to well specifications prior to entering the test design. Fluid and proppant are trapped, and the equipment is disassembled for further analysis after each test. The collected data includes shear rates, fluid viscosities, mean particle diameter, proppant distribution, proppant concentration, pictures and videos.

Observations and conclusions include, but are not limited to, the changes/lack of changes of mean particle diameter of the proppant within the structure, comparative analysis of the carrying capabilities of slickwater, high viscosity friction reducers (HVFR), linear gel and crosslinked gel. Noteworthy differences between 40/70 and 100 mesh behavior are evaluated. An in-depth study on the carrying capabilities of high concentrations of HVFR (4 gpt and 6 gpt) is also included.

The goal of this project is to add further knowledge and insight into the design of unconventional completion techniques and to evaluate new and/or novel proppant and fracturing fluids. With the rapid shift to fine mesh proppants and a lack of comparative production data (ranging from 12-24 months), the industry is relying heavily on research and development to identify effective products for unconventional well completions. These learnings should allow for further development of materials and technologies targeted expressly for unconventional completions.

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