Drilling and completing horizontal wells has become an accepted method to connect natural fracture systems and increase the effective drainage radius. In the Madison formation of the Williston Basin, common practice is to complete the horizontal laterals as open hole. Production is through natural fracture swarms combined with tight matrix permeability. Without stimulation, production has often been disappointing from these wells. During the drilling of the horizontal interval, cuttings are ground into a fine powder. These fines combined with polishing and other horizontal drilling damage mechanisms plug the near wellbore porosity. The fines flow into and effectively plug the natural fracture systems. In order to maximize production rates, some treatment is necessary to remove or stimulate past this damage. This can best be achieved by creating multiple radial fractures or alternately connecting with and widening the natural fracture systems. Several methods have been utilized in the past to achieve this with varying degrees of success.
This paper examines a different approach to this problem. With this process, it is possible to create multiple radial fractures or connect to natural fracture systems in the most promising sections of the open hole. This is done with jointed tubing placement and the use of an oil soluble diverting medium to block acid from reaching previously treated intervals as well as other sections of the open hole. The use of divertor to channel acid combined with conventional tubing diameters allows achievement of significantly higher bottom hole stimulation pressures. The application of this process is presented along with case histories identifying the challenges and the results achieved to date.