Abstract.Corrosion in production tubing strings is seen as a challenging problem in gas wells containing carbon dioxideand hydrogen sulfide. This paper presents a new comprehensive method of corrosion rate calculation with integrated study of reservoir condition, nodal analysis of the well, and well trajectory, which could also have an effect due to the possibility of different flow regimes of the production fluid. This method is applicable to evaluate and predict the performance of selected tubing size and material. This method can also give an economic evaluation for the consideration of using corrosion resistant alloy (CRA) or low-alloy steel and carbon steel. The measurement of corrosion rate can be done by several methods,such as using corrosion coupons, calculating the iron content inside the production fluid, or probes. Either way, when the corrosion rate measured in the field is still below the acceptable maximum corrosion rate, it can be said that the adequacy of this method is guaranteed. This method has been implemented in a gas field,where it successfully selected the best tubing material for the next development well in this field. Consequently, the lifetime of the tubing strings could be extended,resulting in an economical benefit as well.
For the subsea wells, the only accessible annulus is the annulus between production tubing and production casing or liner. When trapped annular fluid heats up, the fluid expands and will increase the annular pressure. Should the annulus between the surface and production casing gets trapped, the pressure buildup on this annulus would put the integrity of the well in jeopardy. In this study, the tubular design approach is used to mitigate the annular pressure buildup by utilizing a section of lower grade casing installed on the outer casing (sacrificial casing) that immediately covers the inner casing being protected and keeps its integrity intact. In selecting the sacrificial casing, three main parameters are needed, these are; the reservoir condition, formation characteristic, and wellbore configuration. These parameters are fed to a wellbore thermal simulator/stress analyses software, in order to create the well model with related pressure and temperature conditions. Iterative annular pressure buildup (APB) analyses throughout the life cycle of the well are then conducted in order to determine the suitable properties of the sacrificial casing. If the property of the sacrificial casing satisfies all expected loading conditions and protects the inner casing string, the design is deemed acceptable and the sacrificial casing becomes a part of the final well configuration. This case study uses a deepwater well in Indonesia in order to apply the sacrificial casing method to mitigate the uncontrolled APB between the 20″ surface casing and 13 5/8″ production casing. A 20″ 154ppf X-56 section was selected as the sacrificial casing. In order to evaluate the effectiveness of the sacrificial casing throughout the life of the well, the various well scenarios covering the drilling operations, production operations and worst case discharge (WCD) events were evaluated. The simulations were conducted using proprietary commercial software having wellbore thermal simulator/stress analyses capability. This study suggests that utilizing a sacrificial casing to mitigate uncontrolled APB is sound engineering approach to keep the well integrity intact.
The biggest challenge for producing a tight (<0.1 mD) gas-condensate reservoir is its low deliverability. Therefore, it is important to consider well stimulation in the field development program. There are several types of stimulation, and one of the types which has the most impact is acid fracturing. However, thorough study needs to be carried out to ensure its compatibility with the specific reservoir condition. This paper will describe in detail how the geology, geophysics and reservoir (GGR) analysis and the stimulation study play its role to create a successful acid fracturing job in Indonesia, specifically in Central Kalimantan. The study begins with the understanding of reservoir geological concept and its characterization using multiple seismic attributes and core sedimentology. This geology and geophysical (G&G) analysis is further enhanced by performing dynamic analysis such as pressure transient analysis (PTA), rate transient analysis (RTA), and flowing material balance (FMB). Following this, feasibility of acid fracturing is assessed by performing the geomechanical analysis and acid solubility test. Moreover, the fracture geometry is also simulated to make sure the resulting fracture is able to penetrate the good reservoir quality. Then, performance projection using reservoir simulation is performed to quantify the expected incremental gain from the job. The geological concept differentiates this platform carbonate into six depositional elements, in which all of the production wells are located in the Reef Complex. It is further defined using the combination of seismic attributes, petrophysical analysis, and production performance, which are able to map the reservoir quality distribution. From the dynamic analysis, it shows that each well has massive connected gas initial in place (GIIP) with several wells are having poor facies nearby that act as the barrier. The study is followed by a stimulation study which shows that the reservoir has hard rock characteristics (Young Modulus up to 3.2 million psi) and high acid solubility (up to 95%), suitable for acid fracturing job. Simulated fracture geometry shows that it could penetrate nearby poor facies and achieve the good facies target. Then, the reservoir simulation also shows that significant production gain could be obtained from the job. Following up on the encouraging result of GGR & stimulation study, the first acid fracturing campaign in this field is sanctioned and performed safely & successfully. It delivers a very encouraging result in which one of the wells shows a productivity increase of up to 200%. Production forecast shows that post-fracturing well performance could sustain the plateau rate up to two and a half years and provide an addition of 25 BSCF of proved developed producing reserves. Material enough for increasing the field profitability and optimizing future development plans. This study shows that understanding the reservoir by doing integrated GGR analysis has significant benefit to reveal the upside potential of the field. Moreover, the excellent result on acid fracturing feasibility study and fracture design prior to the job ensures that it could be performed safely, successfully, and significantly increase the well productivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.