The influence imposed by drilling operations on the outcome of hydraulic fracturing has been well studied in terms of the post-frac stage productivity. Drilling induced formation damage caused by drilling fluids solids and filtration invasion is routinely linked to both the design and the results of stimulation operations in general. Nonetheless, hydraulic fracturing performed on deep and tight sandstone reservoirs presents a new challenge that requires a new perspective when it comes to analyzing the link between drilling and fracturing. The tightness, depth, and highly stressed nature of these formations mean that achieving formation breakdown for the hydraulic fracture initiation is a challenge. To gain a better understanding of this challenge, the role played by drilling in influencing formation breakdown is examined using different types of drilling data pertaining to stimulated intervals.
The proposed examination is carried out by uncovering the variations in different sets of drilling data and correlating those to the results of fracturing. The sets of drilling data considered describe the drilling fluids rheology, drilling fluids interaction with the formation, and the drilled wellbore quality. These observed variations are then investigated through lab experiments where applicable. Other than lab experiments, the links between drilling influences and formation breakdown is established through either data analytics or technical evidence provided by the published literature. Upon establishing the link between drilling influences and fracturing, detailed recommendations are produced to improve the success rate of hydraulic fracturing operations in terms of formation breakdown.
As anticipated, parameters indicating the damage-ability of the fluids used to drill the stimulated intervals showed a clear link to the outcome of formation breakdown attempts. These parameters are mostly measured by the Particle Plugging Apparatus on location prior to and while drilling the intervals of interest. Recommendations to mitigate the effect of these parameters is issued based on a redesigned formulation of the drilling fluid employed. Other influences include certain drilling events that limited the burst pressure rating of the downhole tubulars (casings and liners) to a value below what is necessary to initiate a fracture.
The work presented in this paper has the potential to significantly improve the success rate of stimulation operations in deep and tight sandstone reservoirs. This is proposed to be achieved by uncovering new links between different drilling influences and the formation breakdown. Complementing the outcome of this work with the rich body of literature investigating the relationship between the post-frac stage productivity and drilling can present a new pathway to access reserves in challenging environments.