In the last years it has become technically- and economically feasible to drill productivity enhancing fishbone wells in tight and/or thin formations or in areas where hydraulic fracturing is not permitted due to local environmental regulations. Modeling of fishbone wells is complex and currently very time-consuming. A fully integrated workflow has been developed to model fishbone wells, using dynamic models to generate reliable production forecasts. This novel workflow comprises of the implementation of pre-defined well trajectories and number of needles in a box- and/or full-field dynamic model. Subsequently, the number of needles and number of wells to be drilled is optimized using a workflow driven by project economics.
The workflow comprises the ability to generate forecasts for different well configurations, such as horizontal well length, well depth, number of needles and needle lengths. The needles are modeled explicitly as multilaterals. The needles cannot be oriented during drilling. To obtain a reliable prediction of the recovery of the fishbone wells, a so-called "needle rotation randomizer" has been developed. The orientation of the needles is important in the prediction of future production, as the ratio between the horizontal- and the vertical permeability (KvKh) can be significant in tight formations.
The attractiveness of different well- and needle configurations, as well as the number of fishbone wells is assessed as part of the workflow. This paper addresses how different scenarios, including variation of the number of needle stations (subs) and wells impact project economics by applying a simplified Net-Present-Value (NPV) calculation. Modelling results highlight that more subs will lead to a higher production rate, with corresponding higher NPV's. However, too many subs will lead to lower NPV's, as recovery increase becomes more marginal. It will be demonstrated how modelling can be used to optimize the number of subs. With further full-field dynamic modeling the production forecast can be enhanced by varying well numbers and their spacing the using the optimized number of subs. This paper will showcase how, a fully optimized full field development plan, applying fishbone wells can be generated using the applied workflow in a very short timeframe.
The novel workflow involves the generation reliable production forecasts for fishbone wells, employing a "needle rotation randomizer". Secondly, the new workflow enables optimizing the number of subs and wells, using an efficient economic optimization assessment.