Progressively, the oil and gas industry is producing from unconventional reservoirs with low permeability in numerous small pay zones that require close well spacing and multiple stimulations in each well. To effectively produce from such reservoirs and reduce the surface footprint, ExxonMobil has drilled multiple wells from single pads, and new technologies have been developed to efficiently stimulate the multiple pay zones in each well. ExxonMobil has developed and licensed Multi-Zone Stimulation Technologies (MZST), which are designed to efficiently stimulate wells with multiple pays zones. The technologies have been applied in fracturing tight gas reservoirs with numerous lenticular sands in the Rocky Mountains. We have also developed a technology that enables the simultaneous stimulation of multiple wells on the same or different well pads, and while drilling additional wells. The benefits of this technology include reduced environmental impact, time saving, and improved production rates. Most importantly we have demonstrated that these simultaneous operations can be conducted in a safe and responsible manner to ensure the highest standards of operations integrity. This paper introduces the method and apparatus for this technology and discusses the results from several years of field applications, including the Piceance Basin. Some specific elements of the simultaneous operations safety plan will also be provided. Introduction Worldwide, substantial oil and gas resources are contained in low permeability formations. Many of these resources are characterized by thick intervals and/or multiple reservoir targets. In addition, matrix or fracture stimulation treatments are typically required to effectively and optimally produce these resources. However, the increased geologic and reservoir heterogeneities present in these resources can lead to substantial challenges in the stimulation treatment operations and effectiveness. Over the last several decades, industry has invested substantial research in attempts to develop new drilling and completion technologies for application in tight gas sand reservoirs. Various government and industry studies indicate a vast amount of tight gas resources exist within the United States alone, with similar resources located outside the U.S. Examples of such resources are found widely distributed in the western United States, and include the Green River, Piceance, Wind River and Uinta Basins.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractExxonMobil has developed two novel reservoir stimulation technologies that enable the rapid delivery of numerous highquality stimulation treatments within a single cased wellbore. These technologies were developed for the purpose of improving, or enabling, economic hydrocarbon recovery from formations that contain multiple stacked reservoir intervals or require the stimulation of long productive intervals. These technologies: (1) enable the stimulation of multiple target zones via a single deployment of downhole equipment; (2) enable selective placement of each stimulation treatment so that they may be designed specifically for each individual zone to maximize well productivity; (3) provide positive isolation between zones to ensure each zone is treated per design and previously treated zones are not inadvertently damaged; and (4) allow for treatments to be pumped at high flow rates to facilitate efficient and effective stimulation.

Summary A novel hydraulically powered, self-reciprocating valve pump (SRVP) was piloted in a western Colorado gas well for deliquification operations. The objective was to pump liquids from a deep gas well and later retrieve and redeploy the SRVP without a workover rig. This paper will describe the SRVP technology, areas of applicability, and pilot program, including the completion design, deployment/retrieval workovers, performance, teardowns, learnings, and future plans. Gas-production wells tend to load up with produced or condensed liquids that create an impediment to flow and reduce or stop gas production. Pumps are typically used when the reservoir pressure is too low for less-intrusive artificial-lift (AL) methods or when significant amounts of liquid must be removed. Pumps can suffer from reliability issues and considerable installation/deployment costs because a workover rig is typically required for intervention. Unfavorable producing conditions and tortuous wellbore trajectories tend to further decrease run lives. These issues can make economical hydrocarbon production impossible. The SRVP was developed to overcome these challenges. The SRVP is installed downhole inside a concentric tubing string, and is powered by injecting a high-pressure liquid. The injected (power) fluid causes the SRVP to reciprocate, driving a piston pump to produce formation fluids and to power fluid back to the surface up the concentric-string/production-tubing annulus. The removal of the produced fluids decreases the backpressure on the formation, enabling gas production up the casing. Because there is no mechanical linkage to the surface for pump operation, the SRVP can be deployed in highly deviated and/or small-diameter wells with which standard AL methods would struggle. In addition, the SRVP is designed to be pumped into and out of the well after initial installation, greatly reducing deployment costs. Three industry-first SRVPs were installed consecutively in a concentric flush-joint tubing string, and were powered with a compact surface pumping unit. The SRVP proved the ability to lift 20 to 40 BFPD net liquids up the concentric-string/production-tubing annulus from more than a 12,000-ft vertical depth while gas was produced up the casing. The SRVP was retrieved and redeployed several times either hydraulically and/or with slickline (SL). System design, operation, and performance were continuously improved through the duration of the pilot program. Run life steadily increased to more than 50 days with the third installation.

Just-In-Time-Perforating (JITP) was developed by ExxonMobil over a decade ago to improve multi-zone stimulation in vertical and S-shaped wells in the Piceance basin, Colorado. With this technology, multiple single-zone fracture stimulations are performed on a single wireline run using ball sealers and perforating guns that remain downhole during the fracturing treatment. This results in substantial cost reduction and productivity uplift because perforation intervals are individually and effectively treated one at a time with less horse power, smaller number of frac plugs, and fewer wireline runs. The method has been successfully implemented by ExxonMobil in more than 350 wells and over 10,000 treatments and is licensed to a number of service companies.There is substantial business incentive to implement the JITP technique in horizontal wells, extensively used in unconventional gas developments. With XTO Energy joining ExxonMobil, the global gas portfolio incremented by 45 trillion cubic feet. This includes conventional gas, shale gas as well as other unconventional resources, such as tight gas, coal bed methane, and shale oil. This paper presents the first application of JITP in horizontal wells. Operations were conducted in the Fayetteville Shale, Arkansas. The paper discusses advantages and disadvantages of the method as well as lessons learned from pre-field trials and full-well implementations. Critical to the success of the initial technology application was the enforcement of a structured approach which included technical feasibility studies, contractor qualification, pre-field trials, well candidate selection, and a deployment plan to capture learnings and best practices. Pre-field trials were executed in several wells to test potential technical/operational concerns, such as sand build-up around perforating guns, fluid diversion with buoyant and non-buoyant ball sealers, and the ability to move guns through the lateral. Preliminary field costs and production performance in horizontal wells are promising and support continued deployment of the technology.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractExxonMobil has developed two novel reservoir stimulation technologies that enable the rapid delivery of numerous highquality stimulation treatments within a single cased wellbore. These technologies were developed for the purpose of improving, or enabling, economic hydrocarbon recovery from formations that contain multiple stacked reservoir intervals or require the stimulation of long productive intervals. These technologies: (1) enable the stimulation of multiple target zones via a single deployment of downhole equipment; (2) enable selective placement of each stimulation treatment so that they may be designed specifically for each individual zone to maximize well productivity; (3) provide positive isolation between zones to ensure each zone is treated per design and previously treated zones are not inadvertently damaged; and (4) allow for treatments to be pumped at high flow rates to facilitate efficient and effective stimulation.