Analysis of method for increased field knowledge prior to the field development

Abstract

Field development is an expensive phase with a high uncertainty due to the limited reservoir knowledge prior to field production. Consequently, the field facilities must be flexible to changes, such as: new wellbores, new reservoir pressure support system or others. High field development costs due to flexibility cost and uncertainties in the production, can cause fields to be put on hold or found uncommercial. This master thesis proposes two methods to increase field information that can reduce production uncertainty and the need for flexibility. Proposed method number one is a water injection test that measures reservoir aquifer and complexity, thus help optimize the reservoir pressure support system. Proposed method number two is a 4D seismic reservoir map showing reservoir communication, this can be used to optimize the well trajectory in a complex reservoir. Value of information of the proposed methods are analyzed in two types of reservoirs and in a decision analysis tree. Case results shows that an injection test has a cost of approximately 75 million NOK in an existing exploration well and 4D seismic test a cost of 1,2 million NOK depending on reservoir volume and other factors. The estimated value of information by the proposed methods are 500 million NOK for a low complexity reservoir, and a value of 650 to 960 million NOK in a complex reservoir. This thesis concludes that the suggested methods can reduce the field development cost and production uncertainty while increasing the recovery factor in some fields. The proposed test can increase development of fields that were put on hold or found uncommercial due to a too high risk, development cost or too low recovery factor. The proposed tests are unproven and will therefore have a high uncertainty in cost, time and test results. Limitation of the proposed 4D seismic test is that it can only be performed in a closed reservoir, and water injection test can only analyze one communicating reservoir layer at the time. The further work includes additional cost and risk analysis, reservoir simulations and small scale tests of the proposed methods.