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Unconventional resources in Saudi Arabia symbolize an opportunity to extend required gas plateaus in the long term, to substitute gas for liquid fuels, and to provide potential feedstock for the growing chemical industry. This paper aims to outline an integrated completion engineering and geosciences approach that was applied in the Jafurah shale gas play. The goal was to address complex unconventional reservoirs and their associated challenges, and to determine the optimum completion and fracture design. Sweet spot identification within the Jurassic Tuwaiq Mountain Formation in the Jafurah basin represents a major challenge as it requires a large number of wells drilled over a wide geographical area with high associated costs. This requires innovative drilling, completion and stimulation practices. In order to identify and maximize potential frac stages and placements, a comprehensive study was completed using an advanced workflow encompassing drilling, geophysics, geomechanics, reservoir characterization, completion and fracturing and microseismic monitoring. The targeted Jurassic Tuwaiq Mountain rocks are calcareous and interpreted to have been deposited in a restricted marine environment within an intra-shelf basin. This shale carbonate play shows a high Total Organic Content (TOC), low clay content, good matrix permeability, high gas saturation and high effective porosity. Scanning Electron microscope (SEM) images exhibit a dominant presence of organic porosity associated with the kerogen. Initial results from vertical wells drilled in the Jafurah basin proved that proppant fracturing can be successfully placed, and indicated the presence of a potential gas rich play within the same source rock. Subsequent horizontal wells were the first liquid rich/gas carbonate horizontal wells with ultra-low shale permeability in Saudi Arabia. The first horizontal wells had excellent gas production with significant amounts of condensate. By further building on experience from the drilled and stimulated wells, the lessons learned provide a foundation for the completion of future unconventional gas wells in the Jafurah basin.

Abstract Widely recognized as the world leader in crude oil production, Saudi Aramco has only recently begun to explore for unconventional gas resources. Saudi Aramco started evaluating its unconventional reservoirs to meet the anticipated future demands for natural gas. One of the subject plays that is currently being evaluated is a carbonate source rock with nanodarcy permeability and very low porosity. The target formation has few, if any, analogs that can be used for comparison. Knowledge of the formation characteristics, geomechanics, stimulation response and production potential has been nonexistent until recently. Historically, all attempts to hydraulically fracture stimulate carbonate formations in Kingdom have resulted in premature screen-outs. This paper will discuss the hydraulic fracturing stimulation design, execution and evaluation of the first successful proppant fracturing treatment in an unconventional carbonate source rock in Saudi Arabia. The successful two-stage treatment proved that proppant fracturing techniques could be utilized to stimulate carbonate formations after modifying the stimulation design, specifically the perforation strategy, fracturing fluids and proppant type. The Tuwaiq Mountain and Jubailah formations were treated with 104,000 lbs and 114,956 lbs of proppant respectively. INTRODUCTION Saudi Aramco's unconventional gas exploration efforts were influenced by the growing local gas demand and the economic success of shale exploration in the United States, Canada, Europe and Australia. Saudi Aramco started evaluating its unconventional reservoirs and their potential to reduce oil consumption in the electricity sector and to fuel the anticipated future demands for natural gas. "The multi-stage fracturing technique has facilitated the development of shale gas and light tight oil production in the United States and is believed to do so in the other countries with unconventional hydrocarbon resources" (1). Saudi Aramco has embarked on an unconventional exploration and appraisal project to assess its unconventional resources potential in three geographic areas, Northwest, South Ghawar and East Ghawar. Hydraulic fracturing techniques will be utilized to enhance production by connecting natural fissures and creating high connectivity pathways for gas to flow into the well.

The paper describes the challenges and uncertainties associated with the accurate flow measurement of gas, oil and water and also the results of a trial test conducted using four multiphase flow meters in wet gas-condensate producers at a wide range of flowing conditions. The measurement of these three phases is very critical for the reservoir monitoring and production diagnostics and obtaining the accurate three-phase data poses a significant challenge for the majority of conventional multiphase flow meters, because of the high-gas volume fraction (95 % and above) nature of the wells. Multiphase flow meter technology has been successfully used around the world for over 15 years in oil and gas fields with a very low cost comparing with three-phase test separator use. This success encourages all the manufacturers to continue developing meters; to satisfy and meet the production test requirements and the acceptance criteria established by the operator companies. At the end of 2010, Saudi Aramco conducted a second pilot test to evaluate the four wet gas and multiphase flow meters (WGMPFMs) from various leading manufacturers. The objective of this test was to confirm the accuracy and reliability of these meters for measuring gas, condensate and water flow rates in the wet gas stream. A high pressure test separator was the reference measurement and the test was repeated at several selected gas wells. After almost 4 months, the testing concluded that only a particular type of meter performed better than others and met the minimum Saudi Aramco acceptance criteria in measuring the three-phase flow with acceptable accuracy. This paper also describes the Saudi Aramco’s experience of field testing the latest WGMPFM’s meters in real production condition, field test methodology, equipment setup and result analysis.

Multiple-Stage-Fracturing (MSF) is a common practice today as it allows controlling the stimulation of long intervals, and improves the ultimate recovery of hydrocarbons. Multi-Stage-Frac-Completions (MSFC), designed with Open-Hole-Packers (OHP) and Frac-Ports (FP), are currently implemented by Saudi Aramco to perform such operations in gas wells. The integrity of the OHP and the functionality of the FP are vital for an effective fracturing treatment.During a MSF treatment, the bottom FP is opened first by pressurizing the MSFC to a predetermined pressure. After pumping the first fracturing stage, a ball is dropped to isolate the lower zone, open the second FP with pressure, and enable the second fracturing stage. This step is repeated till all FP are opened and corresponding zones are fracced one after the other. In every step of pressurizing the MSFC, a drop in pressure is automatically interpreted by the assumption that the adequate FP is open and that the MSFC is ready for another fracturing stage. The OHP are also assumed to be holding without performing any downhole checks. Opening the wrong or multiple FP at the same time, having a leaking OHP will certainly lead to undesired results and possible expensive remedial rig interventions. Therefore downhole monitoring is needed to confirm that the MSFC is ready before every fracturing stage.The Fiber-Optic-Enabled-Coiled-Tubing (FOECT) can be used as monitoring system by measuring the Distributed-Temperature-Survey (DTS), which is interpreted realtime to confirm which FP is open, and if OHP are sealing.This paper demonstrates through two case studies how DTS was used to assess the readiness of the MSFC to proppant fracturing treatment. An innovative profiling process in MSFC is proposed to replace assumptions by measured facts, to give client confidence on when to start the fracturing treatment, and to eliminate unnecessary operation by detecting MSFC hardware malfunction.

Gas wells in Field X, south of the giant Ghawar Field, are completed with stand alone screens across a Pre-Khuff sandstone formation as a sand control measure. Although prolific producers, some suffer a severe decline in performance after a period of production, triggering diagnostic work to be performed. Consequently, screen plugging is confirmed and collected samples of present fill are analyzed. Results called for a coil tubing cleanout campaign in order to restore lost productivity. The objective of this paper is to detail the whole operation journey of the fill cleanout jobs that includes fill diagnostic process, assessment of cleanout methods, initial job design, choice of fluids, CT bottomhole assembly tools, execution and field experience, and post-cleanout performance evaluation. A CT wiper trip method has been implemented with either milling or jetting tools. A newly developed rate-activated circulation valve is deployed to aid in lifting solids at high pumping rates as well as jetting acid across the screen interval after fill removal. The fill cleanout campaign has been very successful in restoring well productivity as compared to pre-cleanout and initial post-drilling well performance. A total of 340 MMSCFD of incremental gas rate were restored to-date from 16 cleanout operations. Unprecedentedly, interesting and valuable findings are shared regarding the nature of fill formed inside and/or above the stand alone screens, recommended milling practices to protect CT bottomhole assembly and minimize CT fatigue, the experience of incorporating acid jetting and squeeze in the CT wiper trip method to stimulate damaged formation pack behind the screens, and the preventive measures taken to cope with the fill accumulation issue.

Gas wells in Field X, south of the giant Ghawar Field, are completed with stand alone screens across a Pre-Khuff sandstone formation as a sand control measure. Although prolific producers, some suffer a severe decline in performance after a period of production, triggering diagnostic work to be performed. Consequently, screen plugging is confirmed and collected samples of present fill are analyzed. Results called for a coil tubing cleanout campaign in order to restore lost productivity. The objective of this paper is to detail the whole operation journey of the fill cleanout jobs that includes fill diagnostic process, assessment of cleanout methods, initial job design, choice of fluids, CT bottomhole assembly tools, execution and field experience, and post-cleanout performance evaluation. A CT wiper trip method has been implemented with either milling or jetting tools. A newly developed rate-activated circulation valve is deployed to aid in lifting solids at high pumping rates as well as jetting acid across the screen interval after fill removal. The fill cleanout campaign has been very successful in restoring well productivity as compared to pre-cleanout and initial post-drilling well performance. A total of 340 MMSCFD of incremental gas rate were restored to-date from 16 cleanout operations. Unprecedentedly, interesting and valuable findings are shared regarding the nature of fill formed inside and/or above the stand alone screens, recommended milling practices to protect CT bottomhole assembly and minimize CT fatigue, the experience of incorporating acid jetting and squeeze in the CT wiper trip method to stimulate damaged formation pack behind the screens, and the preventive measures taken to cope with the fill accumulation issue.

The majority of the gas-condensate reserves, currently being developed from fields located in southern Saudi Arabia, come from tight carbonate reservoirs, which require acid stimulation to achieve gas rate targets and field development objectives.Most of the gas producers drilled at the beginning of the gas development program were vertical completions, the majority of which were acid fractured and achieved excellent post-stimulation results. As the development scope expanded to areas with tighter reservoir characteristics, the majority of new wells were drilled as open hole single or dual lateral completions to achieve maximum reservoir contact (MRC). A significant number of these wells did not require acid stimulation, but many others did, either to increase productivity in underperforming wells, or to remove drilling induced formation damage. The most recent approach in the evolutionary process is to drill single lateral open hole horizontal producers and fit them with a completion designed for multistage fracturing treatments.This recent approach has allowed Saudi Aramco to effectively stimulate the entire horizontal section, optimize treatment designs, and achieve excellent post-stimulation results and high gas rates from wells drilled in even tighter reservoirs. This paper describes the historical trend leading to the selection and implementation of multistage fracturing technology as a fit-for-purpose technology to maximize productivity in long horizontal gas producers, and shares post-stimulation results achieved in typical wells drilled and completed throughout the different development phases.

Saudi Aramco has significantly increased the number of horizontal gas producers over the past five years in an attempt to maximize well productivity through maximum reservoir contact while reducing the need for hydraulic fracturing stimulation, commonly required in most vertical producers. Although the majority of horizontal producers have met expectations, a good number of them have underperformed showing lower initial gas rates and higher decline rates than anticipated. The unexpected poor performance in most wells has been attributed to induced formation damage during drilling operations, the highly heterogeneous nature of the reservoir resulting in low porosity and permeability in different areas of the field, destabilization and precipitation of mineral and organic scales in the tubulars and formation, and condensate banking effects.The overwhelming majority of horizontal producers are completed open-hole, which significantly limits stimulation options once the wells have been completed and put in production. Moreover, high pressure and temperature conditions make accessibility of the horizontal section very difficult, and the chance for achieving successful stimulation of the entire horizontal section relatively low. Conventional stimulation treatments involving coiled tubing (CT) acid washes and bullheaded hydraulic fracture treatments have been attempted over the years but results have been mostly unsuccessful or relatively modest.This paper details a case history of a new approach combining different techniques, which was successfully used to stimulate a long open-hole horizontal section in an underperforming gas producer. A hydraulic fracture treatment using hydrajetting technology, that provided the ability to achieve deep penetration into the targeted zone, resulting in effective treatment fluids diversion, was successfully pumped. A detailed analysis to ascertain the effectiveness of the procedure was conducted, the results of which are discussed in this paper.