Porous Limestone Formation Stimulation Using Deep Penetrating Acidizing Technique for Both Injectors and Producers
- Yan Lu (China Oilfield Services Limited) | Da Wang (China University of Petroleum, Beijing) | Jiabo Liang (CNOOC Iraq Ltd.) | Puyong Feng (China Oilfield Services Limited) | Shangqi Shao (China Oilfield Services Limited) | Chao Wang (China Oilfield Services Limited)
- Document ID
- International Petroleum Technology Conference
- International Petroleum Technology Conference, 13-15 January, Dhahran, Kingdom of Saudi Arabia
- Publication Date
- Document Type
- Conference Paper
- 2020. International Petroleum Technology Conference
- undamaged formation, matrix stimulation, limestone, wormhole, deep penetration
- 4 in the last 30 days
- 5 since 2007
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Matrix acidizing is commonly used to enhance the production of damaged wells. As to undamaged wells, it is commonly believed that matrix acidizing can hardly enhance their productivity or injectivity. In Iraq X Oilfield, the acidizing operations for four undamaged wells have failed to enhance their performances, which seemed to meet this assupmtion.
A novel deep penetrating long wormhole creation acidizing technique has been proposed and tested in X Oilfield to stimulate these undamaged wells. In comparison with averaged acidizing technique, it can create a much deeper dominant wormhole by applying a much larger acid volume and pumping rate so as to further enhance the well's productivity or injectivity. Very important, it applies a new type of solvent that can better remove asphalt from the rock surface to facilitate the rock-acid reaction and a retarded acid system to make sure the acid can go deeper into the formation.
This novel technique has been tested in all of the fore-mentioned three production wells and one injection well, which have been failed by averaged acidizing technique before. For these three production wells, the production enhancement ratio after using averaged acidizing technique was only 7% on average. However, the well test result for one of these wells showed that despite the low production enhancement, the post stimulation skin factor is −2.08, which showed that the near wellbore pollution had already been removed by the average acidizing technique. Then they were treated with deep penetrating acidizing technique and the production increased correspondingly. In addition, for the injection well, after averaged acidizing technique treatment, the injectivity index quickly decreased from 252m3/(d.Mpa) to 95m3/(d.Mpa) in only two months. However, after the deep penetrating technique operation, the injection pressure stabilizes at 0 injection pressure for more than 9 months with the same injection rate.
This new technique has been the first time tried in this porous limestone formation to stimulate undamaged wells after the failure using averaged acidizing technique. Though first tried in this Iraqi Oilfield, it can be extraopolated to other oilfields with similar limestone formation around the world.
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