Biopolymer Substitution and Impact on Cuttings Transport of a Lightweight Water-Based Drilling Fluid

Abstract

The aim is to determine the impact of substitution of a local material for another, on rheological properties and hole cleaning capability. A local biopolymer Mucuna solannie was used as a substitute for another biopolymer, Detarium microcarpum, primarily as a viscosifier in a water-based drilling fluid. Tests were carried out using standard equipment and specifications. Variations in transport efficiency and required minimum fluid flow rate at same cuttings concentration (CC) were recorded in the 12¼ in vertical hole section, while in the 8½ in directional section, the maximum ROP that can be sustained while still maintaining adequate hole cleaning was obtained by graphical method. Yield stress values of 2.7, 3 and 12.4 lb/100ft² were calculated based on different approaches. In the 12¼ in section, TE of 99.98% and CC of 5.002 vol.% were observed at 300 ft/h with minimum fluid flow rate of 657 gpm for the Mucuna solannie mud, from a MATLAB cuttings transport program, compared with TE of 99.98 and 98.55% at same CC of 5.002 vol.% for the Detarium microcarpum and XCD/Polymer muds respectively used as control samples. Required minimum fluid flow rates are 612.4 and 621.3 gpm respectively. In the 8½ in section, with the Herschel-Bulkley mud, an ROP of about 8.2 ft/h was obtained as the maximum drilling rate at 40° inclination. The lightweight mud exhibited good cuttings transport in the vertical well, and might not be suitable for highly deviated wells. Comparison of this kind is necessary for evaluation of respective constituents in a mud formulation where several local materials are combined, in a wholly-replaced-bentonite mud. Different models and approaches yielded various yield stress values; hence, comparison of accuracy of models in predicting yield stress is necessary.

Keywords: Cutting carrying index, cuttings transport, lightweight mud, Mucuna solannie