Matrix treatments of horizontal drains in carbonate reservoirs require large amounts of acid, leading to economic-cost and pumping-time considerations. Therefore it is essential to improve candidate selection and to optimize treatment design, especially acid volume, placement and diverting technique.
This paper discusses first, on a theoretical basis, the formation damage effects on horizontal well productivity. Hence, a stimulation strategy is being defined.
The effectiveness of a Self-Gelling Acid Diverter (SGAD) is evaluated by screening the crosslinking conditions with single core flow tests. In particular, the effects of the acid strength in both the diverter stage and the neat acid stage are scrutinized. The diverting effect is also analyzed with a dual core flow apparatus specially designed to reproduce down-hole injection conditions in horizontal wells. The efficiency of the self-gelling agent is evaluated from fractional flow measurements and X-Ray CT visualization of the wormhole penetration. Finally, the study is completed with radial core flow experiments, previously damaged with a drilling fluid.
Design and operational guidelines are deduced from the experimental results and a case history is presented.