Infill Well Modelling in Reservoirs With Multiple History-Matched Descriptions: Case Studies From Andrew and Harding

摘要

The task of selecting and planning infill wells is critical to the ultimate recovery of hydrocarbons from a field, and in a mature basin we have progressed down the long tail of targets to the numerous but small opportunities. There is considerable value left in such targets, even with current drilling technology, but the targets require a better understanding of risk and a higher level of detail. We also face the difficulty this has to occur at a time when the industry is constrained by people resources and rig availability. The Andrew and Harding assets have been leading members of a field trial of a system to test large numbers of alternative depletion plans to try and find the optimum for economic impact and recovery. The assets have also been early adopters of the recent advances in computer assisted workflows, using tools such as BP's TDRM 1 in history matching mode to generate alternative reservoir descriptions that satisfy observations and has some measure of the range in possible outcomes. This paper presents the results of combining infill well planning and multiple reservoir descriptions in a computerassisted workflow of Top Down Depletion Planning (TDDP) 2. The results have enabled smaller targets to be sanctioned, as there has been a better understanding of the risk. Furthermore, instead of appraising three targets in five months of effort, it has enabled the appraisal of seven targets to the same level of detail in only two months of effort, a factor of 4 increase in efficiency for the subsurface team. The case studies have also forced advances in the data analysis, to understand how the infill wells and the alternate reservoir models interact. We can make the choice to seek the optimum choice of things that we can control, such as the depletion plan, on the average performance across the multiple reservoir models that we can't control, but we can use surveillance to try to distinguish between models if we can identify the surveillance prize. The first case study is an introduction to the data analysis of a simple case, looking at the determination of the optimum in a single reservoir model. The second case examines Andrew in more detail, which optimizes on average performance on a range of models constrained by current surveillance. The second study does show the start of a surveillance prize, by showing that some of the different reservoir descriptions actually support consideration of a different depletion plan. The value of surveillance theme is explored in the third case study where we return to Harding and now examine the infill wells when the problem is phrased as the phasing, location and operating conditions of two wells, based on 9 alternative reservoir models.