New oil fields are hard to develop and mature oil fields are becoming more challenging and costly to operate. Advances in multiphase technologies have made significant impact on the way oil and gas companies managing and optimizing their upstream oil business. Multiphase technologies, including multiphase pumping, multiphase flow metering and compact separation systems, have been recognized to provide the critical need to alleviate production decline, optimize production operation, and reduce capital and operating costs. In this regard, Saudi Aramco has undertaken a number of new production related initiatives, developments and projects involving multiphase technologies that are deemed to provide advantages in achieving corporate goals and objectives. The company has invested and implemented significant new multiphase technologies with the goal of maximizing production and minimizing capital investment and operating costs. Multiphase Pumping (MPP) technology provides a cost effective option to develop remote and marginal oil field discoveries. MPP showed excellent performance during field test projects and resulted in significant incremental oil production. Applications of Multiphase Flow Metering (MPFM) technology has resulted in significant capital and operating cost savings. Continuous and real-time data has enhanced production and reservoir management, which led to improved total recovery. Compact Separation technology is another area Saudi Aramco is committed to pursue its field implementation. The technology has the potential to de-bottleneck existing facilities capacity limitation, and reduce facility cost for new oil and gas field developments. This paper will provide an overview of the multiphase technologies Saudi Aramco is considering for field applications. It will also discuss Saudi Aramco's experience and future potential applications. The applications discussed have either been implemented or are expected to be implemented in the near future. Introduction Water cut and gas fraction increase with field production over time. In addition, problems can be compounded by satellite fields located long distances from central processing facilities, and multiphase well fluids transported through pipelines crossing locations with hilly terrain. This is due to the added length of the pipelines transporting the well fluids to production stations or process facilities. There are also specific demands by the process systems in term of the optimum operating conditions. This is often dictated by the characteristics and the operating range of the capacity of the separators in terms of the gas flow rate capacity, the gas compression system and the amount of water they can process as water cut increases.
Acid retardation through emulsification is commonly used in reservoir stimulation operations, however, emulsified acid are viscous fluids, thus require additional equipment at field for preparation and pumping requirements. Mixture of HCl with organic acids and/or chemical retarders have been used developed to retard acid reaction with carbonate, however, lower dissolving power. Development of low viscosity and high dissolving retarded acid recipes (e.g., equivalent to 15-26 wt.% HCl) addresses the drawbacks of emulsified acids and HCl acid mixtures with weaker organic acids. The objective of this study is to compare wormhole profile generated as a result of injecting acids in Indian limestone cores using 28 wt.% emulsified acid and single-phase retarded acids at comparable dissolving power at 200 and 300°F. Coreflood analysis testing was conducted using Indiana limestone core plugs to assess the pore volume profile of retarded acid at temperatures of 200 and 300° F. This test is supported by Computed Tomography to evaluate the propagation behavior as a result of the fluid/rock reaction. Wider wormholes were observed with 28 wt.% emulsified acid at 200°F when compared to test results conducted at 300°F. The optimum injection rate was 1 cm3/min at 200 and 300°F based on wormhole profile and examined flow rates. Generally, face-dissolution and wider wormholes were observed with emulsified acids, especially at 200°F. Narrower wormholes were formed as a result of injecting retarded acids into Indiana limestone cores compared to 28 wt.% emulsified acid. Breakthrough was not achieved with retarded acid recipe at 300°F and flow rates of 1 and 3 cm3/min, suggesting higher flow rates (e.g., > 3 cm3/min) are required for the retarded acid to be more effective at 300°F.
Various acids and chemicals have been developed to achieve retardation properties to enhance oil and gas production. Improving acid retardation through emulsification or polymer gelling agents has drawbacks. Retarded acid recipes including HCl, organic acids, and/or chemical retarders showed comparable retardation efficiency. This paper aims to compare the performance of non-viscous retarded acids and benchmark them against emulsified acids (Hall-Thompson et al. 2020). The proposed acid recipes are either a combination of HCl, formic acid with or without inorganic/organic retarders. Emulsified HCl acids at 15 wt% were prepared as a retardation baseline. Carbonate dissolution was assessed using solubility testing with calcite discs. Coreflood testing was conducted using Indiana limestone core plugs to assess the pore volume profile at temperatures up to 300 °F. This study was supported by Computed Tomography, to evaluate the propagation behavior as a result of the fluid/rock reaction. The solubility calcite discs in the retarded acid recipes showed acid retardation comparable to emulsified acid. The surface tension values of retarded acid recipe were between 19.5-38.5 dynes/cm at 70-300°F. The coreflood results showed retardation performance comparable to emulsified acids at 200 and 300°F. The retarded recipes were capable to prevent nearly 1,500 mg Fe/L from precipitation in spent acid. The corrosion loss and pitting indices were within <0.02-0.09 lb/ft2 using retarded acid recipes at 170-300°F (i.e., <0.02-0.09). The optimum injection rates of retarded acid recipes were nearly 1 and 2 cm3/min at 200 and 300°F, respectively. The results obtained with HCl/Formic acid recipes showed generally competitive retardation performance compared to retarded acid recipes with limitations discussed in the paper.
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