Influence of Temperature Profile Modelling on the Accuracy of Hydraulic Parameters Estimation Effect of Temperature Profile Change Due to Continuous Drillstring Rotation

Abstract

ERD wells are widely used by operators in the MENA region to maximize reservoir contact, lower cost per barrel accessed, and to be able to access far away drill targets from fewer drill centers (wellhead platforms, islands, drill pads). ERD wells and associated required technological well construction approaches by nature are typically non-standard. ERD well construction require very exact and detailed engineering analysis and methodologies to be applied in order to develop suitable and accurate drilling designs that closely matches to the actual conditions. During drilling of ERD wells, a ME operator observed that the static geothermal gradient and subsequent modelling of dynamic flow temperature did not match actual downhole temperatures, hence modifications were required to the temperature profile to match the simulation of OBM drilling fluid ECD (Equivalent Circulating Density) to actual ECD measurements from the ECD pressure sub in the BHA. This temperature effect arises from the several factors, mainly in the sub-surface environment. The resulting mud temperature is significantly higher than static temperature and this has a high impact on mud rheology, resulting pressure losses and hole cleaning. Failure to model correctly can result in mud losses or loss of horizontal section because the ECD gets above formation fracture gradient, to low flowrates for effective hole cleaning due to excessive standpipe pressures, and other problems. This paper presents how hydraulics were modelled to match actual data (rheology, ECD, SPP, BHA, Flowrate, ROP, RPM etc) in one of the longest ERD wells ever drilled. In response to the challenges faced by a ME operator to improve the quality of hydraulic modelling and drilling design, a global Oil and Gas service company and a ME operator jointly explored the approaches for simulating Effective Temperature Profile on the giant offshore oil field, calibrated and verified it along hole with application for providing accurate estimation of hydraulic parameters. The workflow starts from analysis of actual temperature readings in upper sections of the well then uses it for simulating of Effective Temperature Profile in the reservoir section. Then simulated Effective Temperature Profile is imported to the simulation tool for proper drilling design.