Several Decades of Fluid Diversion Evolution, Is There a Good Solution?

The success of any matrix treatment depends upon the complete coverage of all zones. Consequently, the selection of the diversion technology is critical for treatment success. While various types of diverting agents are commercially available, the proper selection of optimal diverter depends on many factors, including well completion and history, compatibility with reservoir and treatment fluids, treatment objectives, operational constraints, and safety and environment considerations. The study will cover five major types of non-mechanical diversion technologies considered as potential solutions for offshore deepwater oil reservoirs: dynamic diversion, relative permeability modifiers (RPM), viscoelastic surfactants (VES), particulate diversion, and perforation diversion. All of them, but a dynamic diversion, are based on different chemicals or products to be added to the injected treatment fluid, and occasionally some can be complementary to each other. Given the offshore and deepwater settings, mechanical diversion techniques were not covered in the study, aiming to find a solution that would achieve acceptable diversion while minimizing operational effort, which would enable riser-less intervention and the use of light intervention techniques. This study was driven by the need to effectively stimulate a 500ft of a cased and perforated interval with a permeability of 500 md, and injection rate limited to 16 bpm due to completion limitations. The sandstone formation, with static in situ temperature of 270F, was far beyond the applicability of dynamic diversion and, to achieve the desired full coverage for the planned scale inhibition treatment required and combination with another diverter system was needed. The process applied included compatibility tests, regained permeability tests, and test well trials. Depending on the specific diversion product analyzed the testing procedures were adapted to obtain the information to properly guide to the optimal solution.

IR 4.0 Technologies Enable Breakthroughs in Upstream Production Operations

The fourth industrial revolution (IR 4.0) has brought about many exciting and game changing technological advancements in recent years that span across different industries. Our petroleum industry was no exception. In this paper, we will present realizations of IR 4.0's fruitful impact on multiple upstream production engineering and operation problems. The first IR 4.0 technology uses machine learning techniques to predict scale inhibition and design inhibition programs that arrest scale formation. Scale formation is a common oilfield problem that consumes a lot of expense from operators. The machine learning method has shown its ability to curtail such expenses and manage risks associated with scale formation. The second technology is modeling the reliability of downhole Inflow Control Valves (ICVs) and predicting their failure. The technology is based on advanced big data analytics and uses automated statistical techniques to achieve the method objectives. This technology provides production engineers with an analytical decision-making model to predict ICVs failures and suggest the optimum frequency for stroking or cycling of the downhole valves as a preventive maintenance practice. The third IR 4.0 technology is the automated well integrity risk ranking. This particular technology uses smart interfaces and advanced computation algorithms applied on big data to assign (or weigh) risks of a well in terms of well integrity. This intelligent integrity ranking or classification shifts focus to wells prone to integrity failures more than the healthy ones. In addition, the method helps optimize integrity surveillance resources and prevents the obvious setbacks from a well integrity issue. The paper will explain detailed methodologies of all three IR 4.0 technologies and outline expected results from field implementation of those technologies.

Game Changer in Dealing With Hard Scale Using a Slickline Torque Action Debris Breaker

Scale deposition is a major concern in Gulf of Suez Fields, variations in water composition and operating conditions resulted in the deposition of full spectrum of scale depositions in different fields. The common practice in GOS is to prevent scale deposition by periodical scale inhibition treatment. However the field experience showed variation in efficiency of inhibition under different operating conditions which results in some cases in scale deposition. In this case we are obliged to react and do intervention to clean out these wells either with chemical dissolution or coiled tubing clean out which is sometimes becomes costly and stand clueless in front of hard scale. Typically, in offshore operating fields, rig-less solutions is the optimum. A simple, innovative, and cost effective Torque action debris breaker tool is a new rig-less solution deployed on slick-line unit. The tool can be run at different sizes to allow for optimum scale removal. Activation is achieved via downward jarring action. The TADB tool applies a new operating concept different from milling. The tool consists of a sharp knife with a broach body. The operating mechanism uses the jarring down action in order to apply jackhammer force on the scale accumulation, which allows decreasing the bond between different layers of scale and between the scale and tubing. Another advantage is having the knife rotating after each jar action, which allows this force to be applied on different positions of scale accumulation adding more efficiency. The tool was first deployed in Egypt in one of the challenging oil wells offshore gulf of suez, which has a historical scale deposition issues "mainly hard deposition of zinc & lead sulfides". several trials were performed to clean out the well historically using coiled tubing operations using barge assist, it took 2 months of operation to achieve partial success & the well was worked over later. The Torque Action debris breaker was tried against the same scale type and found successful. allowing the well to be drifted with 2.7" compared with 2.25" before the job. The operation cost is by no means comparable to the previous cost of coiled tubing operations. Following this wells three other wells were intervened using the same tool and showed much better progress of scale clean out in comparison with other slick-line tools & historical coiled tubing performance in these wells. The implementation of this technology has generally optimized operating cost compared to lengthy and costly CT/WO operation minimizing footprint, equipment, manpower, job duration, and provide a more environmentally friendly solution.

Calcium Carbonate Scale Inhibition with Ultrasonication and a Commercial Antiscalant

In this study, ultrasonication-assisted calcium carbonate scale inhibition was investigated compared with a commercial antiscalant ATMP (amino tris(methyl phosphonic acid)). The effects of varying ultrasound amplitude, pH, and inhibition duration were evaluated. The inhibition of calcium carbonate scale formation was measured based on the concentration of calcium in the solution after subjecting to different conditions. Scale deposits were also characterized using scanning electron microscopy and X-ray diffraction spectroscopy. Inhibition of scale formation was supported at a pH of 7 for an ultrasound amplitude of 150 W. A 94% calcium carbonate inhibition was recorded when the experiment was carried out with ultrasonication. The use of 5 mg/L ATMP achieved a 90% calcium carbonate inhibition of ATMP. The result of the characterization revealed that the morphology of the crystals was unaffected by ultrasonic irradiation. Sample treatment was performed with two different membranes to evaluate the calcium carbonate deposition, and data reveals that, at identical conditions, ultrasonication provides less deposition when compared to the control experiments.

Structure-property Relationship of Flavonoids as Potential Green Inhibitors for Oilfield Scales: A Mini-review

Scale deposits are a significant flow assurance issue in oil and gas operation with huge financial consequences. Not only does scaling drastically impair well performance, but it also has the potential to permanently destroy formation and equipment. Scale inhibitors are commonly used to prevent the accumulation of scales. A good scale inhibitor should be stable at the minimum effective inhibitor concentration under imposed operating conditions without interfering with or being affected by other chemical additives. However, most conventional scale inhibitors that possess these attributes, do not meet environmental restrictions which make them unfavorable for continuous application, prompting the industry to focus more on developing eco-friendly substitutes. This paper reviews the various types of scale inhibitors and general scale inhibition mechanism, summarizes scale concepts and ultimately, assesses the potential of flavonoids from natural plants as potential green scale inhibitors.

New Kinetic Turbidity Test Method and Prediction Model for Calcite Inhibition

Calcite, as one of the most common scales in oilfield can be inhibited by common scale inhibitors. The measurement of calcite nucleation and inhibition is a challenge, because of the difficulty to control pH as a result of CO2 partitioning in and out of the aqueous phase. A new kinetic turbidity test method was developed so that the partial pressure of CO2, pH, and SI can be precisely controlled. Calcite nucleation and inhibition batch tests were conducted under various conditions (SI = 0.24-2.41, T = 4-175 °C, and pH = 5.5-7.5) in the presence of common phosphonate and polymeric inhibitors. Based on experimental results, calcite nucleation and inhibition semi-empirical models are proposed, and the logarithm of the predicted induction time is in good agreement with the measured induction time. The models are also validated with laboratory and field observations. Furthermore, a new BCC CSTR Inhibition (BCIn) test method that applied the Continuous Stirred Tank Reactor (CSTR) theory has been developed, for the first time. This BCIn method was used for calcite inhibitor screening tests and minimum inhibitor concentration (MIC) estimation. By only running one experiment (< 1 hour) for each inhibitor, BCIn method selected the effective inhibitors among 18 common inhibitors under the conditions of SI = 1.23 at 90 °C and pH = 6. It was also found that the critical concentration (Ccrit) from BCIn method has a correlation with the MIC from batch tests. This study provided a simple and reliable solution for conducting calcite scale inhibition tests in an efficient and low-cost way. Furthermore, the newly developed prediction models can be used as guidance for laboratory tests and field applications, potentially saving enormous amounts of time and money.

An Integrated Scale Protection Package for Offshore Fractured Wells Under Designed Shut-In Extension

After fracturing, it is common practice to leave offshore wells shut-in from days to weeks for operational purposes. During the recent historic decline of demand for global crude, a trend has been witnessed to shut in even newly fractured wells under design for an extended period. The cause of these extended shut-ins can be attributed to various factors including operational logistics as well as economic factors. The shut-in extension brings some unique scaling challenges for well designs. In this paper, an integrated scale inhibitor (SI)/fracturing fluid package is presented with detailed laboratory prerequisites data to validate its efficacy for long-term scale protection during the extended shut-in. Utilizing seawater in offshore fracturing can provide significant cost savings to an operation. Unfortunately, in regions with barium-rich formations, the use of seawater brings tremendous barite scaling risk. In order to solve this challenge, the investigation focused on the selection of the most effective inhibitors for long-term barite inhibition under the simulated reservoir conditions. Along with the scale inhibitor selection, the crosslinked gel had to be carefully optimized to eliminate any potential negative interference the gel additives could impart to the performance of the inhibitor. Furthermore, the inhibitor was tested in the crosslinking system to meet optimum rheology requirements. Utilizing the broken gel containing the designed inhibitor package, barite precipitation could be prevented for months under the simulated testing conditions. Due to high levels of sulfate from seawater and the barium originating from the formation, barite scale formed immediately upon mixing of the two types of water in absence of the appropriate scale inhibitors. Solid scale products featuring slow releasing of the inhibitor ingredients was proven insufficient for this application. With extensive laboratory screening, the candidate chemistry demonstrated great brine-calcium tolerance, superior scale inhibition performance for both sulfate and carbonate scales, and the minimum interferences for the crosslinking engineering to meet necessary proppant carrying capacity. To mimic the gel-breaking process and heterogeneous bleeding from the formation water, the inhibitor was crosslinked with the gel at various loading rates (1 gpt to 10 gpt) and broken at the elevated reservoir temperature, then mixed with the different ratios of the formation water. Reliable scale inhibition performance was achieved for an extended period of time for up to six weeks. Incorporating SI into the fracturing stimulation package is a convenient method for operators to include a scale-control program into well-defined fracturing designs with minimal adjustment and also add significant cost-saving for offshore logistics and rig time (Fitzgerald, et al., 2008). The scale inhibitor product presented in this paper shows a superior solution to protect assets from scale deposition for an extended shut-in period.

Development of Fluorescence Tagged Scale Inhibitors for Squeeze Applications in Gulf of Mexico

Fluorescence tagged (F-tagged) scale inhibitors are drawing more interest in the oil industry and are being applied in the field. One main reason is being easily detectable and differentiable from other scale inhibitors. However, when applied to a new oilfield, it is necessary to evaluate their thermal stability, limit of detection (LOD), and fluorescence measurement interference from other chemicals. Two F-tagged scale inhibitors were tested in this study. They are the same polymeric inhibitors with different and differentiable fluorescent tags. Both F-tagged inhibitors were able to be detected in synthetic brine and field brine from a Gulf of Mexico (GoM) field, with LOD of 1ppm. A coreflood test was also conducted for inhibitor squeeze treatment evaluation. The residual scale inhibitor in core flooding samples was measured by both fluorescence method and high performance liquid chromatography (HPLC). The results from two methods generally match with each other. This strongly indicates that the F-tag is stable on scale inhibitors and fluorescence measurement is a reliable method for scale inhibitor detection. Thermal aging test and long storage test were conducted. For both F-tagged scale inhibitors, the thermal aged samples and samples with different storage lifetime did not show significant difference on scale inhibition performance and fluorescence measurement. The two F-tagged inhibitors tested can tolerate high temperature up to at least 130°C (266°F). With proper storage, F-tagged inhibitors after long shelf storage were still as effective as fresh inhibitors. Based on all the test results in this paper, these two scale inhibitors are ready for squeeze application in GoM.