First Evidence for Shale Production Decline Due to Formation Damage Caused by C60+ Paraffin Wax Deposition: A Permian Case Study

Abstract

Abstract Analysis of the production decline curve revealed that the three candidate wells in West Texas depleted faster than a type decline curve, potentially indicating an abnormal permeability reduction mechanism. With the scaling tendency determined to be low to mild for carbonate scale in the formation brine, the use of acids for restimulation was ruled out. However, careful hydrocarbon analysis revealed the presence of a significant amount of heavy paraffin molecules with carbon number higher than C60 that comprise linear, branched and cyclic alkanes. Becasue lighter hydrocarbons permeate faster through the porous media than heavier fractions, dynamic and preferential adsorption-desorption of crude oil components on mineral surfaces account for changes occurring in hydrocarbon compositions during the life of a producing shale oil well. Furthermore, precipitation of heavy organics on the formation matrix could have contributed to the observed permeability reduction and production declines by causing flow restriction in pores and channels and changing wettability of rock surface. With the recent development and utilization of glycolipids, a biosurfactant-based squeeze program was tailored and applied on the three horizontal wells. Forecasted post-treatment production for a 16-month period following treatment was estimated to be 36,500 barrels of oil and 1.391 billion cubic feet of gas. After treatment, over the same period, the facility produced approximately 10,800 barrels of oil and 111,000 thousand cubic feet of gas above the forecasted production volumes, which is a 30% increase in oil volumes and 8% increase in gas volumes. Produced fluids have been collected over the period of 18 months after treatment application to monitor movement of heavy hydrocarbons and residual biosurfactants in both oil and water samples. The impact on improved oil recovery has been very significant with return on investment (ROI) occurring in less than three months.