Drilling-System Optimization Leads to Expedited Wells Delivery

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202172, “Drilling System Optimization Leads to Expedited Wells Delivery,” by Efe M. Ovwigho, SPE, Saleh Al Marri, and Abdulaziz Al Hajri, Schlumberger. The paper has not been peer reviewed. _ The authors write in the complete paper that simple changes in drillstring design can lead to huge savings in a climate requiring a constant push for reduction in well times and well costs and in improved well delivery. The complete paper explains the process that was followed before implementation of this solution. Introduction To access hydrocarbon reserves in a deep gas field, directional drilling through highly interbedded and abrasive formations was necessary. Designing a fit-for-purpose drilling system for optimal performance was critical. The reservoir drainage strategy required that the development wells be drilled directionally to attain a horizontal displacement of 1,500–2,500 ft at the 7-in. liner point above the gas reservoir formation. The well architecture was designed such that the well would be landed in the 8⅜-in. hole section. This required building inclination from vertical (0°) and landing the well at 80° inclination. Then, 4,000–5,000 ft of a 5⅞-in. hole lateral section would be drilled while holding 80° inclination or occasionally building to 90° inclination. Several initiatives had been implemented with the aim of optimizing drilling performance but had not experienced meaningful success in tackling vibration issues. Design Background An analysis of more than 100 horizontal wells drilled on the project revealed that 35% of total well time was consumed in the 8⅜-in. hole section. The majority of this time was spent on slow drilling or remedial operations. It was imperative that the proposed engineered drillstring meet the following requirements: - Able to drill through highly abrasive and interbedded formations - Maintain stability to avoid or reduce stick/slip, shocks, and vibration - Address surge and swab concerns - Minimize exposure through reduced handling - Optimize torque and drag - Optimized based on available tubulars on the rigsite - Reduce flat time Finite element analysis (FEA) and bottomhole assembly (BHA) modeling was performed with these requirements taken into consideration in a bid to generate a fit-for-purpose BHA (Fig. 1). In the deep gas field where the study was completed, the well had to be landed in the reservoir formation and maintain the 5⅞-in. lateral across the entire pay zone. A critical analysis of the formation determined that compressive strength exceeded 30,000 psi and that the formation was highly abrasive. A complete review of the drilling system was completed to optimize the approach to be taken.