It is critical to minimize the amount of free hydrocarbon entrained in the aqueous phase (i.e., Produced Water or Rich Monoethylene Glycol (MEG) streams) in order to mitigate impact on the operational performance of the Effluent Water Treatment and MEG Recovery Unit facilities. Hydrocarbon entrainment in Produced Water or Rich MEG is often the result of process conditions that favour emulsion formation and/or hinder emulsion separation. Consequently there is a need to look at the process and equipment design employed, along the flow path that the hydrocarbon/aqueous phase travels through, prior to entering the separation equipment used for hydrocarbon removal from the aqueous phase, as well as the separation equipment itself. The paper will present a roadmap of the overall route that the aqueous stream can take to offer insight into the process units affected by improper hydrocarbon removal. Operational situations arising from the impact of excessive hydrocarbon entrainment will be given as well as a summary of wellhead operating parameters that need to be considered in terms of their impact on equipment selection/design. The flow path, to be focused on, starts at the reservoir/wellhead and ends where the aqueous stream leaves the final hydrocarbon removal equipment, just upstream of either the Effluent Water Treatment or MEG Recovery Unit facilities. Factors concerning emulsion formation and separation are introduced as required to describe how process fluid properties and flow conditions influence the formation of emulsions and the separation of hydrocarbons from the aqueous phase. How to improve on existing methods for the selection/design of liquid-liquid separators by considering and trying to estimate the entire droplet size distribution (DSD) of the dispersed phase in the stream entering the separation equipment, along with estimating the amount of coalescence, will be elaborated on. This is paramount to ensure the correct equipment is selected, especially when the low end of the distribution, particularly drops below 20 μm, can be quite difficult to remove. Design considerations to minimize hydrocarbon content in the aqueous phase will be discussed and involve looking at key areas of energy dissipation (e.g., choke and control valves) regarding the range of fluid properties and process conditions, and the estimation/influence of drop size distribution/fractional interface coalescence efficiency (fICE) on the selection/sizing of fluid-fluid separator technology. Examples of dealing with emulsion issues occurring in industry, as per vendor experience, will be presented as well as available vendor equipment technology. General recommendations concerning lab bench testing, modelling, and equipment/chemical vendor testing will also be discussed.

ExxonMobil Upstream Research Company (EMURC) conducted a comprehensive laboratory testing program of a produced water de-oiling system primarily targeted for subsea applications. The test program included performance evaluation as well as durability testing of a two-stage mixed-flow de-oiling hydrocyclone technology. The objectives of the test program were to evaluate the separation performance of two system configurations i.e. decoupled and integrated hydrocyclones stages, to understand the overall system integration effects on the performance, and to determine system sustainability to sand loading. Subsea produced water treatment in deeper water applications requires robust, reliable and compact separation equipment. The performance testing confirmed the feasibility of a multi-stage mixed-flow hydrocyclone system for subsea applications and demonstrated that, within a given operating envelope, the system can treat challenging produced water streams with high oil-in-water (OIW) content of up to 5%, reducing it to a few hundred ppm level. In addition, the issue of turndown can be addressed by designing the de-oiling system with multiple parallel banks of liners. The de-oiling system testing was conducted with light and heavy crude oils, of gravities of 36 °API and 19 °API respectively, to map performance characteristics of a two-stage system with the first hydrocyclone stage of bulk oil removal and the second stage of water polishing. Variations in test conditions such as the flow rate, temperature, inlet oil concentration and the reject ratios were introduced to establish optimal operating ranges for each stage as well as for the system. The performance of the decoupled and the integrated system was evaluated by determining separation efficiency break-points at different operating conditions. Accelerated sand erosion tests were performed on a dedicated sand erosion test loop to evaluate different erosion resistant coatings for hydrocyclone liners. The erosion tests helped identify a promising coating solution that can withstand continuous sand loads for long-term operations. The test program demonstrated that a two-stage mixed-flow hydrocyclone de-oiling system can meet challenging subsea produced water treatment and reinjection requirements over a wide range of operating conditions. The paper presents the key results of the overall performance tests as well as the results of sand erosion testing of the hydrocylone liners with different coatings.

For the Santos owned and operated Wortel field, shallow waters offshore Indonesia, there was a need to install compact inline gas/liquid separation equipment with high performance. Due to space constraints, an inline gas/liquid separator was selected. Santos implemented the ASCOM Twinline technology on the platform, which has been in operations since February 2012 and is performing very well. This is an example of rapid technology development, initiated in 2010, with performance verified over a longer period under operations.

No abstract

Deposition formation inside pipelines is a major and growing problem in the oil and gas industry. The optimal use of prevention and remediation tools such as chemical inhibitors and cleaning processes could lead to major savings due to minimized production problems and optimized pipe cleaning costs. This requires characterization and quantification of the actual deposits inside pipelines and downholes. Recently, a novel deposition inline inspection sensor moving inside the pipeline has been proposed based on "inside-out" electrical tomography. In this sensor, the distribution of electrical properties between the sensor and the pipe wall are estimated based on measurements carried out using electrodes around the sensor. In this study, the next generation sensor moving inside the pipeline is described and a deep neural network based approach to deposit estimation is introduced. Test results from a 70 m long semi-industrial scale flow loop containing paraffin wax and calcium carbonate deposits of different thicknesses are shown. Challenges include the changing position and orientation of the sensor during the low. The results show that the sensor is able to measure both deposit thickness and type with good accuracy which indicates that the sensor is suitable for industrial use. Accurate knowledge about deposits allows future blockage prevention, detecting build-up locations in the early phase, increasing accuracy of multi-phase flow and deposition models, optimization of chemical use and validation of deposit cleaning tools before integrity campaigns leading to overall reduced pipeline operation costs.