Method for producing hydrocarbons through a well or well cluster of which the trajectory is optimized by a trajectory optimisation algorithm

A method for producing hydrocarbon fluid through a well or well cluster of which the trajectory is at least partly defined by a well trajectory optimization algorithm that is coupled to a finite difference reservoir simulation program that represents a hydrocarbon fluid containing reservoir as a set of grid cells with a specified permeability and fluid content, comprises:

• providing a virtual well with a series of virtual well branches that extend to inflow points of the virtual well;
• and
• subsequently iteratively moving the inflow points of the virtual well through the reservoir;
• wherein the well trajectory optimization algorithm iteratively moves the inflow points of the virtual well such that a modified well trajectory is defined with a higher Net Present Value (NPV) than its predecessor in order to optimize a reservoir depletion strategy by the well;
• and
• further including the steps of:
• a) defining an initial well trajectory of a virtual well with a series of fluid inflow points in the reservoir;
• b) providing the virtual well with a series of virtual well branches that extend to the inflow points of the virtual well;
• c) using the reservoir simulation program to assign relative impact of all principal virtual well branches on the reservoir depletion strategy, which strategy identifies a life cycle value of the virtual well;
• d) identifying, based on the assigned relative impact, a series of target points to which a series of inflow points of the virtual well should be moved in order to obtain an optimized reservoir depletion strategy that provides a higher life cycle value of the virtual well;
• e) modifying the defined initial virtual well trajectory into an optimized and drillable well trajectory of an optimized virtual well of which a series of inflow points are migrated towards a series of target points;
• f) repeating steps b), c), d) and e) a number of times, iteratively further optimizing the trajectory of the virtual well until a final virtual well trajectory is defined by the well trajectory optimization algorithm;
• g) drilling and completing a well which has the final virtual well trajectory as a target;
• and
• h) producing hydrocarbon fluid through the well from the hydrocarbon fluid containing reservoir.