The Research on Decommissioning and Abandonment Engineering Practice of Onshore Oilfield: A Case Study of Block 1/2/4 in South Sudan

At the end of the lifespan of this onshore oilfield development, all wells and oil production system, transmission pipelines and all surface infrastructures shall be decommissioned in accordance with international guidelines for abandonment of oil and gas facilities. The development and production period relevant to Block 1/2/4 shall be ceased in 2033 as the PSC law approved by South Sudan Government. Considering that South Sudan is located along the Nile River in Africa, necessary measures shall be taken with respect to activities in the field to ensure effective protection for the environment. In addition, difficulties which have negative impact on decommission assessment shall be taken into account, such as inadequate wells data, the destruction of the facility by war, high security risks of Block 1/2/4, costly decommissioning and abandonment fees and so on. This paper combines the practice of Block 1/2/4 in South Sudan to introduce the decommissioning plan, abandonment working process, standard operation procedure for wells and surface facility disposal, and the calculation of the decommissioning fund. The decommissioning may include complete removal or abandonment in-situ which based on an evaluation of cost, safety and environmental impact. While a detailed decommissioning and abandonment proposal has been compiled and updated during the production phase of the project. When the final decommissioning and abandonment plans have been developed for upstream and midstream, the costs have been updated accordingly. These estimates had utilized by the operators to fund the decommissioning and abandonment obligations in accordance with the provisions of the oil company. The D&A task was successful and finally approved by the authority of government. Due to the successful completion of the decommissioning task of Block1/2/4, a completed decommissioning and abandonment management system has been established, including D&A cost calculation and standard operation procedure for wells and facility disposal, which can lower the environmental risk and reduce the capital expenditure at the end of the project. It can be regarded as a classic practice in petroleum industry and has a strong reference value.