Impact Analysis of Different Production History Input Methods on Test Well Interpretation Results for Africa Low Productivity Swabbing Wells

Some blocks in Africa use swabbing for well testing due to low productivity characteristics. As such, the bottom hole flowing pressure does not decrease continuously, but changes in a jaggies pattern with the alternation of swabbing and recovery, which creates great uncertainties in the production history input during well test interpretation and thus affects the accuracy of results. There are three common production history input methods: a. Average production method: the entire production history is averaged and input; b. Swabbing cycle method: the production of each swabbing cycle is input separately; c. Swabbing section and slug flow section method: Input the swabbing section and slug flow section separately for each swabbing cycle. After employing actual well testing data in several Africa blocks, the impact of those methods on well test interpretation has been analyzed with following insights (i) the starting point of the PBU and the rate before PBU have significant effects on the interpretation results; (ii) the impact of three production history input methods on permeability results is negligible (iii) the skin factor obtained by the Swabbing section and slug flow section method is generally appropriate, but the workload of this method is significantly heavier; (iv) use Swabbing section and slug flow section method for the 3–5 swabbing sections before the PBU, while the previous production section uses the Average production method input, can greatly reduce the workload while ensuring the accuracy of the interpretation. Based on the above insights, well test interpretation was conducted on the data of multiple swabbing wells in several blocks in Africa. The practice shows that the interpretation accuracy can be improved without significantly increasing workload, thus making the interpretation results matched better with the actual field characteristics.