In recent years, improved/enhanced oil recovery by tuning the ionic composition of injection water has attracted the attention of the petroleum industry, and currently deemed as new emerging research trend. In view of research results for the last four years, we demonstrated in previous reports (SPE 137634; SPEREE Journal, vol. 14(5), pp. 578-593; SPE 143550, SPE 141082, SPE 154076; SPE 154077) that substantial oil recovery beyond conventional waterflooding from carbonates can be achieved by optimizing the salinity and ionic composition of field injection brine. Similar potential has been confirmed also in the secondary recovery mode. For recovery mechanisms, research confirmed that the driving mechanism is wettability alteration of carbonate rock surface and can be attributed to surface charges alteration, and microscopic dissolution of anhydrite. In this paper, we present the results of two field trials conducted in a carbonate reservoir to demonstrate the SmartWater Flood potential. Both field trials confirmed that in-house research results can be replicated at field scale. Injection of SmartWater revealed a reduction of ~7 saturation units in the residual oil beyond conventional seawater. Considering these field trials are the first-ever applications in carbonate reservoirs, they further provided another confirmation that SmartWater Flood has significant potential to be a new recovery method targeting carbonate reservoirs. A special type of single-well chemical tracer was used in these trials to measure the residual oil in the vicinity of the well following the injection of each water type. During all stages of field trials, careful QA/QC program was put in place to monitor variation in ionic composition in all injected or produced fluids and further insure optimum ionic composition of SmartWater slugs. Several field trials are planned to optimize the current process leading to a multi-well Demonstration Pilot to determine the impact on ultimate recovery and reserves.

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.

No abstract

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.

No abstract