A Novel Technology To Control Proppant Backproduction

Abstract

Summary Back production of proppant from hydraulically fractured wells continues to create operational problems for oil and gas producers. As much as 20% of the proppant placed in the fracture can be returned to the surface, necessitating costly and labor-intensive surface-handling procedures. The development of unmanned platform operations remains impossible in some areas because of proppant back production. Flexibility in well turnaround and production strategies also can be very limited. Curable resin-coated proppant (RCP) has provided the most cost-effective and widely used method to control proppant back production. While this is a valuable technique that has served the industry well for many years, it is not universally successful. A new technology has been developed to control proppant back production and to increase flexibility in well turnaround and production strategies. The technology has been used successfully on several hundred hydraulic fracturing treatments. In this technology, a mixture of fibers and proppant is pumped into the fracture to form a pack that is resistant to proppant back production under typical oil/gas production conditions. The proppant/fiber mixture depends on a physical mechanism rather than chemical bonding to increase pack resistance to flowback. There are no minimum closure stress, temperature, or shut-in time requirements associated with the use of this technology, which increases the flexibility available to the operator to optimize well turnaround and production strategy. This paper reviews the laboratory data relevant to the understanding and application of this technology. Studies include proppant pack resistance to flowback in one- and two-phase flow, the effect of cyclic loading, aging phenomena, permeability/conductivity studies, and fluid/breaker interactions. The benefits of the technology are illustrated with field studies. Introduction Proppant back production has been of concern in hydraulic fracturing for more than 20 years. It has received increased attention in recent years as larger fracture widths and the use of higher proppant concentrations have become more prominent. Back production usually is observed when the well is turned around after the hydraulic fracturing treatment. Back production may stop in time, be controlled by limiting the production rate from the well, or continue through the economic life of the well. Back production from hydraulically fractured wells presents operational problems. It often necessitates costly and labor-intensive surface-handling procedures and on-site control of chokes when beaning up the wells. The erosion of well and surface facilities presents a safety hazard. Proppant remaining in the wellbore can shut off production by covering the productive interval. The magnitude of the problem and the range of viable approaches vary from location to location. As much as 20% of the proppant placed in the fracture has been returned to the surface in Alaska, and as much as 10% is not uncommon in the North Sea.7 Back production can yield as much as 100,000 lbm of proppant. In Alaska, many operators "live with" the problem. In the North Sea, the development of offshore, unmanned platforms is often impossible. Continuous proppant production can sometimes be stopped by producing wells on a restricted choke. In some cases, changes in job design (proppant type, proppant size, final concentration of proppant in slurry, final pumping pressure, forced fracture closure, or lengthened fracture shut-in period) can be effective in reducing or eliminating proppant flowback. The most economical and widely used proppant-flowback-control technique is the curable RCP, which has been the single most effective technology available. Sales of curable RCPs exceed 60,000,000 lbm/yr (and could be significantly higher than that). While curable RCP's have had a great deal of success, they are not, nor could they be expected to be, universally applicable. A new technology has been developed to prevent proppant back production and to allow more flexibility in flowback design and production strategy. The technology relies on a physical mechanism - fiber reinforcement - to increase the resistance of the pack to flowback during production of oil or gas. This report presents laboratory data and field examples of the advantages of this new technology. Its limitations are also presented.

Creating novel granular mixtures as proppants: Insights to shape, size, and material considerations

“…At 6% mixture concentration the number of Al needles is not significantly high enough to disrupt the LWC proppant pack and hence the number of LWC particles fracturing is not as high as in case of walnut. The reason for a less number of pure Al needles is due to their larger density of 2.7 g/cm 3 compared to that of walnut shell which is 1.25 g/cm 3 . The mixtures are based on percentage by weight hence for the same weight percent we should have a much larger number of walnut shell particles compared to pure-Al particles.…”

“…A mixture of hard/brittle and soft/ductile particles, employed as a full proppant pack is found to reduce particle crush/fragmentation while aiding with reduction in proppant flowback [2][3][4]. The softer proppants are generally found to have different shapes compared to the almost spherical ceramic particles, e.g.…”

Mechanics of light weight proppants: A discrete approach

“…Formation of a stable pack is easier with softer rock platens which permits deeper particle embedment [15] iii) Presence of softer deformable particles in the pack increases flowback resistance, but will result in loss of porosity and subsequent loss of fluid flow rate [49][50][51].…”

“…The influence of addition of softer particles to a proppant pack on pack permeability has been studied extensively and a reduction in the flow rate has been observed [49][50][51][52].…”

“…A modification to the conductivity test wherein an arrangement is made to collect loose proppant and measure their flow rate is used to study proppant flowback. Several researches have focused on understanding the factors affecting proppant flowback and finding ways to reduce it [14,15,[49][50][51][52]. Apart from the DEM (discrete element method) simulations by Asgian [14] the rest focus on experimental approach.…”