Sustained Annulus Pressure (SAP) is a common production constraint in the oil and gas industry, it is usually caused by impaired seal Integrity within the wellbore system resulting in barrier failures. In peculiar scenarios the thermal expansion creates pressure build-up in the annulus as well which can equally impair the integrity of the wellbore. In this paper the results of downhole and surface pressure monitoring surveys are presented, the objectives aim at determination of both downhole leaks and verification the influence of thermal expansion into a wellbore system integrity in a field located onshore Niger Delta. SAP in a producing well was earlier recorded during routine annular pressure monitoring in 2017 during the production rate increase by changing the bean size from 18/64" to 24/64". Initial diagnostics observed pointed towards SAP resulting from a possible downhole seal integrity issue leading to a leak to the surface. While putting the well on stream with current bean size and the pressure regime for both THP and CHP was observed. Pressure with time analysis showed annulus pressure builds up rapidly while flowing and bleeds off within 30 min from 700 psi to 0 psi when well shut in. Downhole logging and sensitive passive acoustic monitoring was conducted, the survey aimed to detect barrier failures by capturing its acoustic leak patterns under shut-in and bleeding off condition. Considering the suspected leak behaviour, the data acquisition included the procedure to build up the annulus pressure by flowing the well and monitoring the annulus discharge. Integrity logs survey and passive acoustic monitoring confirmed there were no downhole failures and after several bleed-offs when Tubing choke was beaned down to 18/64" no annulus pressure build-up was observed from the Well head gauge on the Casing head confirming the source of the sustained annulus pressure is driven by the temperature expansion of the annulus fluid. Remedial action and recommendation after Simulation were to de-risk the well at a controlled bean size to mitigate SAP and optimally flow the well.

Often, the production of oil and gas from underground reservoirs is accompanied by produced water which generally increases with time for a matured field, attributable to natural water encroachment, bottom water ingress, coning effect due to higher production rates, channeling effects, etc. This trend poses a production challenge with respect to increased OPEX cost and environmental considerations of treatment/handling and disposal of the produced water considering the late life performance characterized by low reward margins. Hence, produced water management solutions that reduce OPEX cost is key to extending the field life whilst ensuring a positive cash flow for the asset. SK field is located in the Swamp Area of the Niger Delta, with a capacity of 1.1Bcf gas plant supplying gas to a nearby LNG plant. Oil and gas production from the field is evacuated via the liquid and gas trunk lines respectively. Due to the incessant tampering with oil delivery lines and environmental impact of spillage, the condensate is spiked through the gas trunk line to the LNG plant. Largely, the water/effluent contained in the tank is evacuated through the liquid line. Based on the availability of the liquid line (ca. 40%-60%), the produced water is a constraint to gas production with estimated tank endurance time (ca. 8 days at 500MMscfd). This leads to creaming of gas production and indeed gas deferments due to produced water management, making it difficult to meet the contractual supply obligation to the LNG plant. An interim solution adopted was to barge the produced water to the oil and gas export terminal, with an associated OPEX cost of ca. US$2Mln/month. Upon further review of an alternate barging option, this option was considered too expensive, inefficient and unsustainable with inherent HSSE exposure. Therefore, a produced water re-injection project was scoped and executed as a viable alternative to produced water management. This option was supported by the Regulators as a preferred option for produced water management for the industry.

The ability to perform remedial activities to enhance production from existing wells in order to extend field life is an essential component of brown field management. Predicting the movement of hydrocarbon/water behind casing and estimating remaining hydrocarbon column ensures economic value on proposed activities can be quantified. Fluid contact measurements over time are useful for tracking reservoir performance, planning work over and enhanced recovery strategies, as well as diagnosing production problems such as water influx. This paper highlights the value of integrating pulsed neutron log data with other subsurface data and models to provide a robust solution in well intervention. The case study demonstrates how pulsed neutron log data has helped resolve multiple challenges such as; Estimation of remaining hydrocarbon column and volume, perforation placement uncertainty, optimizing reservoir block development strategy and ensure robustness of reservoir dynamic models. Results from the case study show that integrating pulsed neutron log data in a work-over intervention could amount to huge cost savings (>$10,000,000 dollars in this case) in proposed operation. Additionally, calibration of acquired log data with existing dynamic models led to perforation optimization which gave resource volume increase of about 15% from two reservoirs against pre-estimated volume.