As part of the stimulation plan to obtain the optimum slickwater frac design in the main source rock play in Saudi Arabia, a series of systematic trials were carried out testing different frac design parameters, such as the proppant volumes and types, and fluid & additives volumes (friction reducers, spearhead acid etc.). These trials were carefully designed in several 4-well pads across the field, comparing different designs in wells next to each other in the same pad, to allow consistency in reservoir and geology conditions allowing the trials to be conclusive. Wells were flowed back for a relatively short period of time and different production analysis techniques were used to compare the different designs against the standard.
In this paper, the Normalized Initial Productivity Index of the wells was compared using the Gas, Gas Equivalent, Total Fluid Downhole Flow Rates Productivity Index (PI), and the Effective Fracture Lengths from rate transient analysis were used to help on selecting the optimum frac designs. In these trials, other important completion parameters were kept constant: the number of clusters per stage, cluster spacing, type of perforation guns, frac fluid and proppant type. The flowrates are measured using the three phase separators and the corresponding bottom-hole flowing pressures are estimated using multi-phase flow parameters, and the matched wellbore hydraulic models. The reservoir pressure is estimated from the pressure decline analysis of the frac stages along the lateral.
The results show that there was almost no change in the productivity results by lowering the proppant volumes 25%. The results also show that better wells are obtained by lowering fluid volumes by 33% and decreasing the additive volumes by more than 75%. Overall, the improved PI obtained with lower proppant and fluid volumes and less additive concentrations, provided an optimized frac design that is being carried into the development phase wells.
This paper helps in understanding and maximizing the productivity of the wells and optimizing the design including chemicals, to capitalize the value generation from the individual wells on the multi-well pads.
