Abstract Reservoir sands in the deepwater formations in West Africa are largely soft and unconsolidated based on data from producing fields and preliminary studies on upcoming developments. Studies have shown that fractured injection in unconsolidated sands is different from hard rock fracturing in which case a single dominant fracture is created during injection. For unconsolidated sands, smaller fractures are created to bypass impairment and much of the injection may be under matrix rather than fractured conditions. Given the importance of waterflood to most projects, it is imperative to understand the dynamics of fractured injection in this type of sands and all the factors that can impact on the effectiveness and efficiency of designed waterflood systems. This is even more important for upcoming projects whose viability may depend on the delivery of high rate – high ultimate recovery wells which can only be supported by an effective pressure maintenance /voidage replacement system. In this paper we present a study carried out on one of such developments (turbidite reservoirs in Deepwater West Africa) for which a water injection program is to be designed. The modeling work is highlighted and the effect of different parameters on fracture growth propagation and injectivity were analysed.
Abstract Bonga oil producer wells are capable of delivering high rates in excess of 20 Mbopd; thus, any breach of well safety critical barriers could potentially lead to significant people asset and environmental damages. In addition, deferment caused by well integrity would also significantly impact production. Therefore, well integrity management remains an integral part of Shell's "Must Wins" and the Bonga team is focused on ensuring that we can demonstrate that the Bonga wells remain "safe and healthy" while delivering against production targets. One of the key challenges faced in the deepwater environment is the prohibitive high cost of rig intervention for diagnosis and remediation of well equipment failures; hence the well integrity management approach in the Bonga field places a lot of emphasis on use of alarm settings to operate wells within defined operating envelopes; proactive monitoring of the well operating parameters and consistent high compliance on preventive maintenance. This has resulted in the early detection of well integrity issues and minimal shut-in periods of wells for well integrity related failures. Also, innovative and cost effective methods of integrity repairs using an ROV deployed by the field intervention vessel have been implemented in the Bonga field. This article describes the application of Well Integrity Management in the Bonga deepwater environment and highlights some of the challenges and lessons learned in safeguarding the integrity of deepwater wells through the operational phase.
Abstract The Bonga field has produced more than 275 MMstb in the last 4 years, a major contributor to deepwater oil produced offshore Nigeria to date. High production rates are being sustained as a result of the pressure maintenance scheme based on waterflooding that was implemented from the onset of production. Fully treated seawater is injected from 13 subsea high rate water injector wells daisy-chained on two separate water injection lines. To date more than 370 MMbbls of treated seawater has been injected in the field. High rates in water injector wells can only be achieved through fractured injection. Industry experience so far shows that matrix injection mode leads to declining well injectivity. However, for effective reservoir management, it is required that fractures created are not excessively large to cause integrity concerns on nearby seals, reservoirs and wells. Hence, it is necessary to predict the fracture dimensions for corresponding injection rates and pressures for effective waterflood management. The size (length and height) of an induced fracture depends on several parameters. This paper describes the use of an in-house fractured injection tool for estimating lateral and vertical extension of waterflood-induced fractures in Bonga wells. History matching of field data is performed to calibrate the model. Information from Pressure Transient Analysis and well interventions is used to improve model prediction. The analysis shows that with continuous high rate injection, long contained fractures are created in these high Darcy sands. Prediction results are used to define operating envelopes for these high rate water injector wells, with rates constrained in some wells to prevent induced fractures breaching the top shale layer.
Abstract The introduction of the "Drilling in the 90s" concept resulted in the loss of the Well Site Petroleum Engineer (WSPE) position on rigs, which hitherto was the generally accepted development format for graduate recruits in the Petroleum Engineering function in major IOCs through the ‘70s and ‘80s. A two-year stint as a WSPE on drilling and workover rigs was usually followed by development opportunities in one of the PE disciplines with an opportunity to grow into a PE technical professional. A review of job competence profiles performed around the middle of last decade among young to mid level Petroleum Engineering professionals showed deficiencies in skill levels due to limited exposures to field operations at the Young Technical Professional (YTP) level following the discontinuation of the programme; new joiners into the PE disciplines remained office based in respective asset or discipline teams, going into the field for visits to learn or witness specific drilling and field operations which usually focused around discipline interests and generally lacked structure, depth and the required levels of exposure to field operations. In order to address this problem, the WSPE programme was reinstated to bridge skill gaps by field exposure, thereby producing more competent YTPs prepared for growth up the PE career ladder. This paper presents a review of the competency gaps observed with the suspension of the WSPE programme and describes the WSPE & Field Exposure model adopted by Shell Nigeria, which is considered a key element in developing competent PE's through a structured exposure to the practical aspects of oilfield operations in the first two years of their career.
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