No abstract

Repsol (operator), together with partners Petrotrin and National Gas Company of Trinidad and Tobago, took over operations of mature fields Teak, Samaan and Poui (TSP) Offshore Trinidad at the end of 2005. With the intention of planning further development in the TSP reservoirs (comprising more than 10 vertically stacked main units, highly compartmentalized reservoirs with complex tectonic geometries) an indigenous comprehensive field evaluation was required. Thus, a sand-by-sand Screening Project was carried out with the main objective of identifying the reservoirs with maximum potential so as to direct further technical effort on specific reservoirs for early monetization of reserves.Based on the results of the sand-by-sand screening project, a prospect validation project for Teak Field was initiated -consisting of extensive field data acquisition, detailed interpretation and modeling workflows, adapted to the particular needs of mature fields. Several incremental opportunities identified during screening were validated and detailed modeling was performed to support further development. On completion of this effort, the company acquired a holistic view of the asset in terms of projects and its remaining resources, so a drilling campaign was envisioned and planning started.The selection of drilling candidates was not a straight forward process. The number of opportunities had been reduced considerably from the opportunity category to the actual well candidates. Several disciplines developed specific workflows to overcome the challenges, for example: risk assessment for infill opportunities and probabilistic forecasting (Subsurface), trajectory designs including anti-collision, drilling through depleted sands, torque and drag analysis and selecting a suitable rig for the field and production platform conditions (Drilling Engineering); among others.At the time of submitting this paper, two drilling rigs are moving onto the acreage to start drilling these opportunities by the end of 2013. This paper outlines the different challenges faced, as well as case studies of the evolution and maturation from the screening to the drilling stage of some of the prospects.

Repsol (operator), together with partners Petrotrin and National Gas Company of Trinidad and Tobago, took over operations of mature fields Teak, Samaan and Poui (TSP) Offshore Trinidad at the end of 2005. With the intention of planning further development in the TSP reservoirs (comprising more than 10 vertically stacked main units, highly compartmentalized reservoirs with complex tectonic geometries) an indigenous comprehensive field evaluation was required. Thus, a sand-by-sand Screening Project was carried out with the main objective of identifying the reservoirs with maximum potential so as to direct further technical effort on specific reservoirs for early monetization of reserves. Based on the results of the sand-by-sand screening project, a prospect validation project for Teak Field was initiated – consisting of extensive field data acquisition, detailed interpretation and modeling workflows, adapted to the particular needs of mature fields. Several incremental opportunities identified during screening were validated and detailed modeling was performed to support further development. On completion of this effort, the company acquired a holistic view of the asset in terms of projects and its remaining resources, so a drilling campaign was envisioned and planning started. The selection of drilling candidates was not a straight forward process. The number of opportunities had been reduced considerably from the opportunity category to the actual well candidates. Several disciplines developed specific workflows to overcome the challenges, for example: risk assessment for infill opportunities and probabilistic forecasting (Subsurface), trajectory designs including anti-collision, drilling through depleted sands, torque and drag analysis and selecting a suitable rig for the field and production platform conditions (Drilling Engineering); among others. At the time of submitting this paper, two drilling rigs are moving onto the acreage to start drilling these opportunities by the end of 2013. This paper outlines the different challenges faced, as well as case studies of the evolution and maturation from the screening to the drilling stage of some of the prospects.

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.

This paper presents a methodology for the probabilistic analysis of an infill or step-out opportunity using numerical simulation. Sensitivity and uncertainty analyses for all involved parameters were evaluated through different experimental design techniques. Subsequently, a proxy model was established to reproduce the numerical model performance. Finally, three appropriate solutions were selected from a large population of realizations corresponding to probabilistic percentiles (90%, 50%, and 10% certainty that the specified volume will be recovered). This proposed methodology helped the asset team to evaluate the well candidates more precisely, confidently, and in less time than the current standard methodology. More knowledge about the variables and their effects on overall outcomes was also gained, which helped the team make more-informed decisions. The workflow used the same numerical modeling software, incorporating and facilitating the changes of both static and dynamic properties simultaneously. A case study from Teak field, on the east coast of Trinidad, illustrates the applicability of the methodology and compares its results to those obtained using the standard workflow for the asset. The methodology is one of the latest developments in reservoir simulation, and it has not yet been incorporated into the operator's common practices and procedures for exploitation of the TSP fields.