This paper presents the experiences of well clean-up operations carried out in the development wells of Akpo deepwater field. Akpo is located 135 km offshore Nigeria in 1400 m of water depth. The reservoirs consist of faulted, unconsolidated, turbiditic channel and lobe sands with complex architecture. The fluids in each reservoir are near-critical. The field is currently producing about 175,000 barrels of condensates per day. Current sand control techniques are Frac-Pack (FP), Stand Alone Screen (SAS) and Expandable Screen (ES). Early data acquisition during well clean-ups was essential in other to optimise the development strategy, ensure a production ramp-up in line with expectation and reduce remaining uncertainties which were mainly linked to sand communication within channel complexes, fluid behaviour, and faults behaviour (seal or conduit). The paper covers the clean-up design, execution, operations monitoring, data acquisition, and fluid sampling, along with the challenges and constraints encountered in the process for the different wells. It describes how the challenge of hydrates formation, exacerbated by the deepwater environment and peculiar nature of the reservoir fluid, was handled to ensure successful well clean-ups. It also gives an example on how the early data acquisition program impacted important field development decisions.

Many of the water injectors in sand control environments are being completed as long open holes due to higher injectivities attainable with such completions. Although target rates may often be achieved without any cleanup chemicals in production wells, injection wells require filtercake cleanup, in cases where • producing the well prior to injection is not feasible or desirable, (e.g., limited storage capacity on the rig, or artificial lift requirements due to low pressure or injection into water leg) • injecting above frac pressure is either not feasible (e.g., very high frac pressures and pump limitations) or not acceptable (e.g., sweep efficiency, premature water breakthrough, uncontrolled fracture height growth).Although a large variety of filtercake cleanup techniques and chemistries are available in the industry, most of these solutions are effective in producers. As demonstrated through laboratory experiments, achieving consistently high injectivities requires removal of drill solids from the filtercake, through either dissolution (e.g., acid formulations utilizing HF) or effective displacement techniques that will not result in injection of these solids into the formation pore throats (SPE 77449). In addition, an effective filtercake removal (including drill solids) in long open holes without inducing high losses into the formation (so that the wash pipe can be pulled out and a mechanical fluid loss control valve can be activated) remained as a formidable challenge, which becomes even a bigger challenge in wells drilled with conventional oil based muds (OBM), particularly in reactive shale environments.In this paper, we present a novel technique that addresses these challenges, proven through field application on a standalone screen water injector in Nigeria. The technique involves displacement of OBM from openhole with a viscous spacer pill containing a demulsifier, followed by completion brine containing a mutual solvent to weaken the filtercake without attacking the bridging agents, subsequently performing a high rate viscous pill displacement to remove the external cake, and finally spotting a water-based self-destructive fluid loss control pill to control the losses while pulling the wash pipe. Laboratory testing for designing the displacement stages, field execution, and well performance evaluation are detailed.

The oilfield Tchendo, located 18 miles off the coast of the Republic of Congo, has been operated since 1991 by Total E&P Congo in depths of approximately 100 meters of water.The shallowest of the three reservoirs, the Sénonien reservoir (400 m TVD SS), involves an intercalation of carbonate layers with thicker (5 to 15 meters) but poorer quality siltstones.Various attempts to enhance productivity on existing wells were unsuccessfully carried out since initial production, including selective or extensive perforation, acid treatments on the carbonate layers, and, in recent years, hydrajetting fracture stimulation on three wells.Although the field is non-conventional, so far, it has been developed conventionally. A large amount of the original oil in place still remains in the reservoir. To make the redevelopment project viable, a step change in stimulation techniques is to be undertaken.Two workovers were performed at the end of 2012 as a "proof-of-concept". Innovative fracturing technologies, including hydrajetting, were combined to deliver a non-sleeve scenario for horizontal well multi-stage fracturing. The workovers resulted in the largest fracturing treatment executed by Total on an offshore well. This paper reports on the lessons learned in the process of fracturing this non-conventional reservoirs that will be capitalized for the future redevelopment of the project.

Expandable screens are a relatively new technique in the industry. Recently, three typical cases of expandable screen applications were presented in the SPE paper 121543. The present paper focuses on deepwater case histories of expandable screen applications within TOTAL. Deepwater projects are challenging, high profile jobs. Reliability and robustness are key factors in selecting the right sand control techniques. So the benefits of using of expandable screens must be plain so as to offset the reluctance of introducing this relatively new technique. Large deepwater developments started for TOTAL in 2000 in West Africa. On those projects and since, the typical development scheme for unconsolidated, uniform, medium-size sand fields, has been: - Horizontal oil producer completed with Stand Alone Screens. - Deviated oil producer completed with either Stand Alone Screens or Frac-Pack completions (depending on reservoir characteristics). - Horizontal and deviated water injector completed with Stand Alone Screens. That typical deepwater scheme now introduces expandable screens in: - water Injectors for deviated wells, and - oil producers for deviated wells. This paper offers feedback and insight on case histories from West African projects. It details the installation process (mud, cake treatment, and expansion aspects in application from floating rigs), the limitations and the performances.