Abstract
In order to counter-balance the formation pressure, the drilling mud is weighted up using a chemical additive, usually Barite. The usability of locally sourced Nigerian Barites on the major types of drilling fluids in conventional conditions is presented. Water-Based mud, Oil-Based mud and Synthetic-Based mud formulations with locally sourced Barite were tested according to the American Petroleum Institute recommended practices. Hole cleaning capabilities of the formulations by the use of Cutting Carrying Index (CCI) and Cutting Concentration (CC) as indicators showed that Osina, Gabu and Obubra Nigerian Barites are suitable for use as drilling fluid additives; with Cutting Carrying Index in the range of 23.27 to 120.54 for Water-Based mud, 0.89 to 3.98 for Oil-Based mud and 0.45 to 1.13 for Synthetic-Based mud. The Cutting Concentration of average of 4.15 vol. % at 355gpm and 300ft/hr ROP for Water-Based mud, Oil-Based mud and Synthetic-Based mud, with MAXROP of 364ft/hr under the same conditions was recorded. Moreso, laminar flow regime in the annulus was predicted for all the mud types under the same conditions and temperatures specified, based on a MATLAB programme developed to perform the computation. Cutting Carrying Index for water based mud decreased from ambient, 120°F, 180°F to 240°F compared with API mud used as control sample.
Highlights
Nigeria is one of the highest crude oil exporting countries in the world and has various ongoing exploration and production activities
This study aims to determine the usability of Nigerian barite as an additive in different types of drilling fluids that can be used especially in high temperature and high pressure environments as compared to imported barite
Lower grade barite of 3.6-3.8 Specific gravity can be used but will require a larger quantity of the mineral to weight up the mud as desired
Summary
Nigeria is one of the highest crude oil exporting countries in the world and has various ongoing exploration and production activities. In order to produce crude oil, wells are drilled into the formation either as exploratory, production or appraisal wells. These wells must be drilled to satisfy three basic conditions;. A borehole is said to be stable when the formation pressure is less than or equal to the hydrostatic pressure. Drilling operations conventionally operate on an overbalance where the hydrostatic pressure is maintained slightly above the formation pressure. Where the hydrostatic pressure is lower than the formation pressure, the borehole is exposed to well problems such as sloughing, kick or blowout. Drilling a hole involves penetrating through several strata of formation and requires special technique to economically and safely reach the target depth
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