Waterflooding is commonly performed in oil wells for pressure support and increased oil production. Different sources of injection water can be used for waterflooding, such as aquifer water, seawater or produced water. Each of these water sources contain particulates in them that deposit at the injection point forming both an external filter cake on the reservoir face and an internal cake inside the rock surface. The properties of the external and internal filter cake negatively affect injectivity. In order to identify the optimum water filtration specs prior to injection, the contribution of different solid particle types present in the injected water on filter cake properties and injectivity need to be understood. A lab study has been undertaken to gauge the contribution of different solid types, solid sizes, and the presence of oil droplets on filter cake properties and water injectivity. The solid types tested were silica/quartz, clay, iron oxide, barium sulfate and calcium carbonate, with and without oil contamination. Membrane tests were conducted to understand the correlation between the porosity and the permeability of the external filter cake that forms at the formation face for each particulate type. A heavy slurry of selected solid particulate was mixed in brine and was compressed into a membrane under different applied pressures, and the porosity and the permeability of the cake was calculated at each stage. Core tests were designed to look at the combined effects of the external and internal filter cake on reduction in injectivity. Outcrop cores, representative of the field cores, with similar pore throat size, porosity and permeability were used in the core tests, as particle bridging at pore throats is a function of the comparison between the injected particle size and the pore throat size distribution of the reservoir. A slurry of the selected solid particulates in brine was injected into the core system and the permeability drop across the core was monitored as a function of injected water pore volumes. Both types of tests were repeated in the presence of oil contamination in the injected water. The test data from the membrane tests and the core tests were used in the numerical model to obtain the permeability reduction function for the internal and external filter cake.

The development activities of CABGOC Block 0 pose various challenges to completion design. Multiple types of reservoirs are encountered, while it is also critical ensuring field development remains economic. Completion standardization has been an important tool to maximize operational efficiency and reduce costs of installation. Nonetheless, given the variety of reservoir types found in the area of operation, few completion types are required to solve most of the cases. Despite of having successfully implemented completion standards in several types of reservoirs, there was a gap on the type of completion to efficiently drain multilayered fine particle reservoirs with sanding tendencies. These field characteristics make standard completion techniques difficult to deploy, therefore a novel conformable sand screen solution was selected for a field trial. This paper describes the plan, preparation, execution, and the results of the conformable sand screen deployment in CABGOC's N'Singa field. Furthermore, it demonstrates how effective the conformable sand control technology can be established for a multi zone open hole type of reservoir. Integral zonal isolation and flow control of various zones provided flexibility in production management for a four well campaign. The Shape Memory Polymer (SMP) conformable sand screen technology was key to produce sand free from the fine particle sands in this marginal field in Cabinda Province offshore Angola. Unlike the conventional sand control technique, the conformable sand management system selected for this field trial leverages a unique SMP material that expands downhole in the presence of an activation fluid and conforms to the borehole wall. Compatibility and expansion tests were conducted in the planning stage to validate screen conformance with selected completion fluids. Tests were also used to define deployment procedures and optimal fluids management practices for the completion operation. Installation was successful on all four wells as per plan. All equipment and fluids were managed and operated efficiently with flawless execution. The wells were brought to production and the results confirmed the effectiveness of the technology in terms of sand retention, and completion efficiency during production. The project was concluded with significant reduction in rig time, personnel requirement, fluid management, and pumping operations. This allowed for selective production of reservoir that would not have been possible with standard techniques. Additionally, the obtained results facilitated the decision to implement conformable sand screens as standard completion design for other fields in the reservoir with similar challenges as those observed in N'Singa.

For nearly every producing field worldwide, acid stimulation is a type of intervention that is critical to longevity in production (or injection) for those wells. However, compared to other completions/intervention operations (e.g., cementing and hydraulic fracturing), several deficiencies have been identified in the historical training curriculum for acid stimulation. Legacy acid stimulation training is largely focused on the basic aspects of matrix stimulation, excluding many practical and contemporary topics. The current work details the development of an innovative, operations-focused training program for acid stimulation intended to augment historical training. To commission the development of new stimulation training curriculum, stakeholders from operations, management, and the technical function (subject matter experts) brainstormed the most critical needs for practical training that would add value to operations beyond current internal/external training material. From this, customized training material was built that includes new focus areas including a) Mature well stimulation: workflows were developed to prioritize likely types of damage that cause productivity/injectivity decline based on existing well data. These workflows led to further training regarding damage-focused stimulation design (rather than pure matrix/mineralogy-based design), to optimize stimulation/fluid selection to target specific damage in mature producers. b) Complex well stimulation: this includes customized training material related to stimulation of existing sand control completions, infant wells (unproduced), and laminated carbonate/sandstone pay zones. c) Operational considerations: this new training material addressed operational best practices including topics on specialized placement methods; on-site QA; and interpretation of pressure data (during stimulation). d) Practical experience: the last aspect of the new training material includes students designing acid stimulation treatments for real candidate wells. The new operations-focused training material was piloted with several operations teams in 1-week intensive sessions, following the first week of (existing) basic acid stimulation training. This training (deployed both in-person and remotely) was well received by both the operations management and the students, who noted the enhanced relevance of the new curriculum to the production enhancement plans for the wells for which they are responsible. Additionally, the interactive team-activities to design stimulation programs for challenging wells (challenging mineralogy and existing sand control completions, multiple damage mechanisms, and wellbore mechanical obstructions) helped to improve acidizing designs for actual candidate wells through feedback from other students and class mentors. This work highlights the development and implementation of new training curriculum for acid stimulation design and execution, developed to improve the practical skills of production engineers and operations teams that design acid stimulation operations. Deployment of this new curriculum will help to improve the probability of success in acidizing some of the most challenging well conditions.