Enhancing Proppant Flowback Control Through Surface Treatment of Proppant

Abstract

Post stimulation proppant flow back has long been an issue of the hydraulic fracturing process. The most common means of remedying proppant flowback has been to treat proppants with a resin coating. However, the most daunting factor in using resin-coated proppants is the resulting high price, which can be in excess of four times the price of untreated proppants. Additionally, resin coated proppants often need to be activated with exposure to temperature and pressure. In the case of low temperature/low closure stress reservoirs, additional chemical activators are required which further increases the cost. A proppant flowback control measure which is cost-effective and can perform over a wide variety of reservoir conditions would be advantageous to the hydraulic fracturing process. A new technology has been developed to control proppant flowback that is a non-toxic, cost effective, and operationally easy. After being coated with a proppant consolidation aid (PCA), the proppant depends on a physical mechanism rather than chemical bonding to increase proppant pack resistance to flowback. There is no minimum closure stress, temperature, or shut-in time requirements associated with the use of this technology, and the coating can be applied to all or just selectively some of the proppant stages, which allows more flexibility available to the operators in flowback design and production strategy. Laboratory testing will illustrate the efficacy of sand consolidation using the PCA coating. Simple lab bottle consolidation testing will demonstrate a comparison between untreated and treated proppants. Large scale tubing flow tests will also demonstrate the ability of the coated proppant to resist movement during fluid flow relative to untreated sand, and will also show the cleanup ability of the sand at higher flow rates in the event of a sand-off where proppant remains undesirably in the wellbore. Other testing will reveal additional benefits to the sand treatment such as improved sand pack conductivity and increased compressive strength. Computed Tomography (CT) analysis will be used to explain one of the mechanisms that results in increased proppant pack conductivity. Temperature stability testing will be included to show the wide potential application window of the PCA chemistry.

Quick Determination of the Optimal Fracture Filler for Hydrauilc Fracturing

“…• Большая тенденция к выносу в неглубоких скважинах с малыми стрессами, а также неравномерное распределение проппанта по трещине с образованием пустот, пропусков, островков проппанта [10].…”

“…В статье [10] показаны результаты лабораторных работ по определению характеристик специального состава, наносимого на проппант. Данный состав консолидирует обычный проппант путем склеивания зерен друг к другу.…”

“…В полевых условиях имеется риск несовместимости геля с данной добавкой, что требует обязательного тестирования на совместимость. По заявлениям [10], химический состав значительно дешевле ПП. Основные условия применения показаны в таблице 1, строка 6.…”

A model of the proppant flowback: setup of the theoretical framework

“…In addition to the above-listed reasons of flowback following from the experimental results presented in literature [Vo et al 2014;Lu et al 2016], the form and coating of the proppant grains affecting the internal friction forces between individual proppant particles have a significant effect on the removal process, which in turn affects the stability of the proppant pack. Furthermore, from experimental data and from results when modeling the proppant removal process by the distinct element method, it follows that the packing becomes unstable, starting with a certain ratio of the average grain diameter to the width of the crack opening.…”

“…where σ r is the closure stress. Many authors note that this stress affects proppant flowback and consider it as one of the main terms to control the proppant flowback [Milton-Tayler et al 1992;Asgian et al 1995;McLennan et al 2015;Andrews and Kjørholt 1998;Canon et al 2003;Aidagulov et al 2007;Vo et al 2014;Lu et al 2016;Barree and Conway 2001;Larsen and Smith 1985;Ely et al 1990]. The value of the closure stress is significant enough to hold the packed proppant in the fracture even when the outgoing force is big enough.…”