This paper will focus on a new resin technology that improves proppant flowback control under extreme conditions. The combination of dual phase flow and pressure drops in high rate gas wells has made proppant flowback a significant problem. These conditions must be addressed to maximize well productivity and minimize production costs. Moreover, the problems associated with cyclic stress effects can further hamper well production and tax any technology controlling proppant flowback. The most commonly applied proppant flowback control technology is the use of curable resin coated proppant (CRCP) either entirely or as a tail-in for hydraulic fracturing treatments. CRCPs have an established history in the consolidation of proppant packs under defined conditions of time, temperature, and closure stress. Improvements in CRCP performance have been facilitated by use of a new resin system through chemical and process changes. These changes have enhanced resin bond strength (RBS) characteristics commonly measured as unconfined compressive strength (UCS). Data shows RBS is anything but the dominant trait in preventing proppant flowback. This is most evident when the proppant pack is subjected to a large pressure drop, Non-Darcy multi-phase flow, temperature, and cyclic stress. Further associated effects are prolonged pumping time and elevated temperature exposure during CRCP placement. The CRCP placed under these conditions is subjected to elevated temperatures while the proppant is transported into the fracture and before fracture closure. CRCP performance testing in the laboratory can accurately depict these effects. A new resin technology is presented that is specifically designed to withstand the aforementioned conditions. The performance benefits are documented by rigorous laboratory testing (under simulated downhole conditions) and case history data from stimulation treatments performed on deep, high flow rate gas wells. Introduction Numerous references to the need for proppant flowback control in high rate wells and the consequences of proppant back production have been published.1–4,8 Loss of fracture connectivity to the wellbore and the resultant loss of productivity, potential damage to surface production equipment and the related safety issues, plus the waste of time and resources make proppant flowback control critical in maximizing the NPV of a well. The demand for reserves from deep, lower permeability, high temperature reservoirs in South Texas and the Gulf of Mexico5 has dictated that sophisticated proppant stimulation is required to achieve economic production levels. Bottom hole static temperatures (BHST) for producing formations in South Texas can average between 149°C and 232°C. Wells in the 166°C BHST range are now quite common. CRCPs have had great success in HT/HP applications where the proppant placement and fracture closure times were modest. In other work, Underdown13 taught that modified phenolic resin coatings are stable to at least 300°C. As cost-effective deep, slim hole and tubingless completions in South Texas and the Gulf of Mexico have become more common, the slurry pumping rates that proppant can be placed have been greatly reduced. Combined with the longer fracture lengths and associated fluid/proppant volumes that are required, the total job pump times can run several hours. Additionally, due to the lower permeability of the formations, fracture closure on the proppant due to fluid leak off may take hours instead of minutes.
A new phenolic resin system has been developed for proppant consolidation when fracturing low temperature wells. Before the development of this new resin system, which was in response to a global industry need, external chemical activators were necessary to achieve sufficient bond strength of the resin coated sand pack (when treating wells with bottom-hole temperatures less than 140°F). This new low-temperature cure system develops superior proppant pack bond strength and requires no external activation at temperatures as low as 100°F.Eliminating the need for external activators not only decreases the complexity of the fracturing treatment, but also contributes to the saving of time, money, and decreases the need for chemical transportation and the associated potential hazards.However, the lower operating temperature limit of this resin chemistry can be extended even further with the addition of an external chemical activator. The paper will discuss product performance data that was generated to document the effectiveness of this technology at simulated downhole conditions. Results from the initial field trials utilizing the new Low Temperature Resin Coated Curable Proppant (LTRCCP) in various shallow wells in the Permian Basin will also be presented. Field trial data resulted from thirty-nine treatments that were performed on a total of twenty-two wells, in nine different producing horizons, spread over four different fields in Southeast New Mexico and West Texas. The Information presented describes formation properties, treatment designs, post fracturing production response and lessons learned. Introduction Curable, phenolic resin coated proppants (RCPs) have been successfully used in the prevention of proppant flowback and prop pack rearrangement for more thantwenty-five years [1,2,3,4].Loss of fracture connectivity to the wellbore and the resultant loss of productivity is important in lower temperature applications as well as the more notable higher temperature applications [2,3,5].At lower temperatures (<140°F), various external chemical activators have been used for the last twenty years to help the resin coating develop higher grain-to-grain bond strength[1,2,6].However, in many field applications it is common practice to flow wells back immediately following the completion of the hydraulic fracturing operation.In this situation, external chemical activators can be run with curable RCPs even at temperatures up to 160ºF.Without the use of an external chemical activator, and depending on the proppant mesh size and thus the number of contact points, the useful and measurable proppant pack consolidation strength development of the conventional curable phenolic resin proppants in water at lower temperatures(<140°F) can take ½ to 5 days as the temperature approaches 100°F [1,6]. Alberta Province in Canada, the Permian Basin in West Texas/New Mexico, Alaska, and the Northeast U.S.A., along with Western Siberia in Russia are areas where large amounts of RCPs can be used at lower temperatures.The combination of shallow depths, and waterflooding or CO2 flooding of mature oil producing reservoirs, can provide challenges to develop the necessary RCP pack strength without the aid of an external chemical activator.
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