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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 postfrac stage productivity and drilling can present a new pathway to access reserves in challenging environments.
Al-Haj, Hussain (Kuwait Oil Company) | Al-Ajmi, Abdullah (Kuwait Oil Company) | Gohain, Ashis Kumar (Kuwait Oil Company) | Al-Rushoud, AbdulAziz (Kuwait Oil Company) | Khatib, Faiz Ismail (Kuwait Oil Company) | Soliman, Ahmed Hussein (Baker Hughes) | Al-Mujalhem, Manayer (Baker Hughes) | Fathallah, Mohamed Omar (Baker Hughes) | Ibrahim, Ahmed Samir (Baker Hughes)
It is a challenge to drill in highly deviated or horizontal holes with high differential pressures. Wellbore instability, differential sticking and mud loss are frequently encountered problems while drilling slanted wells in Kuwait across shale and sand series. Drilling became more challenging with considerable non-productive time. Therefore, it is necessary to identify a fluids solution when other options with casing zone isolation are not viable. Traditionally, oil-based mud (OBM) was used while drilling these formations with limited success.
A customized fluid system was designed to overcome the issue of high overburden pressure in shale and sand series formations targeting effective bridging, minimizing pore pressure transmission, and strengthening the wellbore. A nano-size deformable synthetic polymer, along with sized calcium carbonate and graphite, was identified to effectively plug the pore throats and minimize fluid invasion, which was confirmed by particle plugging tests.
A well section was identified to comingle the highly depleted and pressurized formations. This was the first attempt on a high-angle well with development drilling operations in Kuwait and was performed to facilitate the successful drilling of the reservoir. Traditional OBM was converted to a customized fluid system using a nano-size polymer and sized bridging additives based on proprietary software selection and a series of laboratory tests. Drilling and logging were successfully performed for the first time in the commingled section without incident. There was no wellbore instability or differential sticking tendencies, less torque and drag, as well as enhanced wellbore cleaning in the high-angle sections.
This paper also presents some successful applications of the nano-size deformable polymer in OBM to drill highly depleted formations in HTHP wells managing up to 3500 psi overbalalnce across highly permeable formations.
Qingyang, Wen (China University of Petroleum) | Xiujuan, Yang (China University of Petroleum) | Xiangzhen, Yan (China University of Petroleum) | Gensheng, Li (State Key Laboratory of Petroleum Resource and Prospecting China University of Petroleum Beijing)
Analysis indicates hydrates can occupy as much as 500 m of sediments.