With the increasing energy demand and call for cleaner energy, industry has ventured out for challenging environment such as deepwater and unconventional natural gas resources. While new development is necessary, improvement in gas supply can also be achieved by relooking into the current system. Currently, associated gas produced from oil well are mainly used in petroleum operations, while the remaining gas are either flared or vented to the atmosphere. Inefficient usage of associated gas which has high heating value impose a great value leakage to the company.
This paper introduces a new concept that demonstrates more efficient usage and monetization of gas by utilizing associated gas and non associated gas based on its composition instead of volume and sales agreement. The value addition of this new concept was evaluated across the process chain from the upstream operator, host authority, to the downstream plant processing and end product at customer level, using a case study at Field A and Field B.
Field A is a brownfield which utilizes produced associated gas for petroleum operations including gas reinjection. Field B is a non-associated gas green field which is tied in to Field A’s processing facilities prior to gas export. Both gas from field A and field B were evaluated based on their gas composition, gross heating value and customer requirement to determine the best option of gas utilization to maximize its value. Feasibility study was carried out to ensure the practicality of the job execution and at the same time commit to the legal and sales requirements.
Field A and B belongs to the same PSC, and gas sales are purely based on the heating value and contractual volume requirement. Hence, Field B lower heat value gas can be used for injection provided that the similar volume was replaced for sales. The gas swapping for optimization can be conducted through simple flowline modification with minimal cost. A portion of gas from field B will be directed for gas reinjection at field A, while the associated gas at field A originally intended for injection will be utilized for sales. Injecting gas with leaner hydrocarbon composition will not hinder the oil recovery efficiency of field A. However, gas sales using associated gas from field A allow additional 11% profit gain for the operator from existing scenario. The products of processing the swapped associated gas will reap more profits to the downstream sector, as the gas has higher ethane, propane, and butane molecules.
In the current situation, existing fields have always considered gas utilization individually. There is potential for all fields to utilize gas more effectively to increase the economic value of the field and downstream facilities.