Hideharu Yonebayashi

Ready for Gas Injection: Asphaltene Risk Evaluation by Mathematical Modeling of Asphaltene Precipitation Envelope (APE) With Integration of all Laboratory Deliverables

An offshore carbonate oil field in the Arabian Gulf is exhibiting asphaltene deposition problem mainly inside tubing of production wells completed in one of two main producible limestone reservoirs. This problem significantly reduces well profitability due to production loss and frequent asphaltene removal job (solvent soaking). Furthermore, future full-field EOR development, namely gas injection, is now planned and might have a risk to enhance the asphaltene problem. Therefore, comprehensive study has been carried out not only to establish less frequent and more effective remedy than the current action but also to evaluate a future risk of gas injection. The study was initiated with careful review of the fundamental measurements, collected during the 20 years production history, of asphaltene properties, i.e. SARA (saturates, aromatics, resins and asphaltenes) analysis, asphaltene contents, AOP (asphaltene onset pressure) measurement, etc. Subsequently, the mathematical modeling analysis using those properties was incorporated into the study in order to develop APE (asphaltene precipitation envelope) for better understanding/predicting of asphaltene precipitation behavior. Therefore, this paper describes the integration/optimization of the APE modeling based on all available laboratory data, and consequently suggests representative APE. The APE model validity was evaluated by comparison with actual observation data in the problematic reservoir. Based on the mathematical models once established, several sensitivities, namely mixing with injection gas and blending oils produced from two main producible reservoirs, were investigated in order to assess impacts of the future EOR on asphaltene risk from sub-surface and surface point of views. Several types of injection gas were examined, and their risks were compared and identified. Consequently, the surface facility design was adequately modified and optimized in order to minimize asphaltene risk assisted by gas injection.

Managing Experimental-Data Shortfalls for Fair Screening at Concept Selection: Case Study To Estimate How Acid-Gas Injection Affects Asphaltene-Precipitation Behavior

have complexity of technical evaluation. Such complexity might be encountered when assuming an emerging condition or when introducing emerging technologies. In such cases, potential concepts are often difficult to evaluate fairly with existing technologies, but can possibly be evaluated with newly introduced or developing evaluation measures. However, these new and developing measures require cost that can be justified at the matured stage of development, but that cannot be justified at the concept-screening stage. In the future, the exploration and production (E&P) industry will be required to access more emerging fields of lesser easy oil; thus, this case study will be an example engaging a similar situation.

Safety for a Helicopter Load/Unload Operation on an Offshore Platform: Optimization From Several Viewpoints and the Psychological Aspects of the Marshaller

Field and Logistics. The field is located offshore, approximately 200 km (108 nm) away from the nearest airport. Flight time is 1 hour and 5 minutes in still air by a twin-engine medium-sized helicopter with two blades that has a cruise speed of 100 knots. In the case of a four-blade twin-engine helicopter with a cruise speed of 125 knots, flight time is 52 minutes in still air. In the case of vessel transportation, it takes 1 day from the nearest port. The field has been developed with facilities consisting of a central complex with living quarters and surrounding unmanned platforms. All wells are tied-in platforms. Produced fluids are sent to the central complex through subsea flowlines. The central complex has both a helideck and large crane equipment, while the platforms have a helideck and simple human-powered hoist equipment only, without any crane equipment. Regular or ad hoc but prescheduled material transportation is performed by an offshore support vessel between the nearest port and the central complex, except urgent/emergency transportation. Once materials arrive at the complex, the method of transportation from the complex to the platform depends on the situation. If there are small materials that can be managed by human carrying or lifting with simple hoist equipment, then those materials are transported by supply boat. Heavier materials that cannot be lifted by human power are transported by helicopter. There are three types of platforms—one-leg, three-leg, and four-leg. The number of well slots and the size of the helideck increase with the number of legs on the platform.