Evaluation of Local Viscosifiers as an Alternative to Conventional Pac-R

Abstract

Hole cleaning is a key parameter in every drilling program. Efficient bottom hole cleaning is achieved through adequate transportation of cuttings from the wellbore to the surface. Modified natural polymers like Poly anionic cellulose regular (PAC-R), with bentonite clay has been used to achieve good carrying capacity of drilled cuttings in water base mud (WBM). These conventional polymers have adverse effect on the environment, especially the mud-filtrate which pollutes and contaminates the aquifer and the spent mud that requires caution for its disposal. In this work, Local viscosifers were obtained from Mucuna Flagellipe (Ukpo), Brachystegea Eurycoma (Achi), Afzelia Africana (Akpalata) and Detarium microcapum (Ofor) as a substitute for the imported viscosifiers (PAC R) used as a drilling fluid additives. Water-based muds were formulated from the aforementioned locally sourced viscosifiers and that of the conventionally used viscosifier (Pac-R). Laboratory tests were carried out on the different muds formulated and their rheological properties evaluated, such as yield stress, , shear stress plastic viscosity and shear rate. The concentrations of the locally sourced viscosifiers were varied and rheological tests performed show that Mucuna Flagellipe (Ukpo) had a better viscosity compared to Achi, Akplata and Ofor of the same concentration. It was also observed that 5g of Mucuna Flagellipe (Ukpo) and 8g of detarium microcapum (Ofor) gave an equivalent rheological properties of 27lb/100ft2and 26lb/100ft2 as yield stress when compared to2g of Pac-R which gave a yield point of 29lb/100ft2 at a temperature of 180˚F. Also, 8g of Mucuna Flagellipe (Ukpo) gave an equivalent of 5g of PAC-R. Hole cleaning parameters such as slip velocity, annular velocity and cuttings transport efficiency were also considered for evaluating the effectiveness of the proposed muds with local viscosifiers and conventional viscosifiers on hole cleaning. 5g and 8g of Mucuna Flagellipe (Ukpo) compared favourably with PAC-R in terms of hole cleaning. Finally in terms of cost, the locally sourced viscosifiers are cost effective when compared with the conventional vscosifier. Therefore, locally sourced viscosifiers (Mucuna Flagellipe, Ukpo) can be used as a substitute to the conventional Pac-R when drilling top hole at a temperature of 150˚F and below since these holes are drilled within a thermal gradient of 150˚F and below in the Niger delta region of Nigeria.