| Popis: |
Formation damage by Fines Migration is one of the leading causes of loss of productivity in oil and gas wells. Oil field operators report significant losses which can sometimes reach 100% as a result. This is one main reason why operators around the world carry out well interventions in the range of hundreds of thousands of dollars in order to improve wells’ productivity or bring them back to production. Well XX, one of the most prolific producers in a field in the Niger Delta area of Nigeria began to experience noticeable decline in wellhead pressure and oil production as soon as spikes in water production were observed. Shortly after this observation the well quitted and was later shut in. Wireline re-entry, BHP survey, Wax and Asphaltene studies and others were conducted to ascertain the root cause of the problem while elimination method led to the suspicion of fines migration. The well was then lined up for acid stimulation. The well was stimulated with a Coiled Tubing unit using Regular Clay Acid (RCA) as the main treatment fluid as advised by the contractor. The well was restored to production after the entire activity and well cleanup. This improvement in productivity was followed by high water cut and increase in well head pressure to its initial value. After the successful stimulation exercise, the well pressure and production were observed to drop continually while BS&W was on the increasing trend. Soon afterwards the well status returned to initial and a second stimulation was planned for the well. The second stimulation was planned with understanding of the type of migrating clay which necessitated a change of recipe for the stimulation. This paper details the issues with the well before stimulation, results of studies that were conducted, the first stimulation exercises - results, analysis of post stimulation data and planning and success of second stimulation. |
