One of the most critical issues in TSP fields is the unconsolidated character of its sands. Historically, most of the wells drilled in TSP fields, including vertical, deviated and horizontal wells, have been completed with cased hole gravel pack (CHGP). However, over the course of the years, these completions have been known to fail eventually, especially in the case of horizontal completions. Among the failure reasons are the complexity of such operations and the drawdown applied during production. During the last drilling campaign in 2014, a horizontal well was completed with open hole gravel pack (OHGP). In addition to the change of completion, the production strategy was also modified to delay the water breakthrough and reduce the drawdown. These changes have significantly contributed to increase the production of the asset and opened the opportunity to apply these changes in wells for future campaigns. The horizontal well, was drilled through unconsolidated sand (Pliocene), where continuous fluid losses were expected to be encountered. During the well project execution it was necessary to create a mitigation plan in order to minimize the risk of fluid loss (rate) circulation before running the lower completion. For this it was necessary to include an isolation valve to control the losses once the packer was confirmed to be set. Normal reservoir pressure, and available facilities, was key factor to decide to include a gas lifting system in the upper completion which was also designed to have the maximum ID as possible for future intervention jobs such as acid stimulation and logging operations. Finally the well was successfully completed in OHGP with no signs of bridging. Based on the results obtained a complete detailed analysis for the pre and post job will be exposed in this document. This paper outlines the different challenges faced, as well as to highlight the action plans, mitigations and lessons learned encountered during the planning, design, and execution of the completion phase. In addition, a review of the production history of similar completions and the production strategies followed will be discussed. Finally, the results of this well will be summarized and lessons learnt shared.
Teak, Samaan and Poui (TSP) is a mature field off the South-East coast of Trinidad, which currently produces near to 14,000 bopd with an average Water Cut of 85%. In production since 1972, it peaked at 143,300 bopd in 1978. Repsol E&P T&T has been looking to increase oil recovery by unlocking the remaninig potencial of their reservoirs in Sands 01, 02, 1/2 and 2. An interdisciplinary and detailed study was generated between several disciplines, including geology, petrophysics and reservoir engineering, to re-evaluate these sands, where a waterflooding project had been implemented between the 70's and 90's with seemingly good results. A Static Model was generated starting from a detailed well by well analysis (well logs and core information, seismic, production and pressure data, etc…), where some problems, related to uncertantly in the Structural Model and to the interpretation of the input data had to be overcome. This paper explains the workflow that was used to create this static model. First, the originally suspected several Oil Water Contacts (OWCs) had to be analyzed. The area is affected by several fault blocks with varying juxtaposition of the geological layers, which lead to the interpretation, in previous studies, of several contacts. A solution to this and to the effect that this juxtaposition has in the flow within the reservoir and in the pressure distribution is analyzed in this paper. The next step was to reach to a rock type definition based on k/phi relations and a J Function (J(Sw)), with the challenge of having insufficient Core Data and Pc curves. An additional challenge faced was the questionable resistivity logs, which are suspected to have been affected by drilling mud throughout the successive drilling campaigns. Then, in order to define permeability and water saturation models, an alternative workflow was tested and implemented. This method includes conventional rock typing analysis (Pc derived J(Sw)) and extrapolation of these results to the wells. This, together with the resistivity logs (Sw), has been used to compute permeability above the OWC. Threrefore, this allows us to calculate permeability first, and then use it in the J function to calculate the water saturation that will be input into the model. Finally, a Lorenz plot was built to define flow units and identify the possible water injection paths.
Teak, Samaan and Poui (TSP) are mature fields off the South-East coast of Trinidad, which currently produce near to 14,000 bopd with an average Water Cut of 85%. Their production started in 1972 and peaked at 143,300 bopd in 1978. The 0/1L Sand, in the Teak field, has accumulated over 72 MMBO and displays a low reservoir pressure, yet it still contributes with almost 10% of the total current production of TSP. Secondary recovery was implemented in TSP since the late 1970s; some 21 MMBO are estimated to have been recovered from Sand 0/1L, in the Teak Field, thanks to the Water Flooding campaign, which was active between 1977 and 1998. Repsol E&P T&T ltd., operator of the TSP asset, has identified the potential for increased oil recovery by means of waterflooding. Evaluating injectivity of those wells that are available for injection is the starting point of the current strategy. Additionally, Repsol's Technology Center in Madrid has been contacted to perform a specialized water characterization and compatibility analysis, which is currently ongoing. The focus of this paper however is the subsurface. Initially, the reservoir pressure and production behaviour has been analysed to estimate pressures and analyse block connectivity. Together with this a first one-dimensional material balance model was created to preliminarily evaluate performance. A multi-layer Water Flood pattern simulator, which has proven very useful in understanding past performance, was one of the main tools of the analysis. Finally, a full 3D model is currently being tuned to obtain definite production profiles. Furthermore, the value of detail model preparation was proven by the identification of potential workover candidates. Remaining oil was identified in bypassed areas and in zones previously interpreted as gas bearing. The main goal of this paper is to understand past performance of waterflooding as the key to defining the remaining potential.
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