EFFECT OF HEMATITE ON YIELD POINT OF WATER BASE MUD

Abstract

Abstract: The aim of any drilling operation is to provide a path way or conduit from surface to depth of interest which
would later facilitate the production of the formation fluids. In order to achieve this, petroleum drilling engineers do
incorporate the best of drilling practices in which drilling time is a critical factor. Drilling cost is directly proportional
to time spent on drilling the well and as such any parameter that would drastically increase the drill cost is critically
analyzed with the view of getting the optimum conditions for such parameter. Rate of penetration have been known to
affect drill cost significantly. In order to optimized the rate of penetration and minimized torque during drilling, the
hole must be adequately cleared of drill cuttings. The hole cleaning properties of the drilling fluid are essential to
achieving the set objectives. Drilling fluids play important roles in any drilling operations. These roles are not limited
to controlling formation pressures and lifting of drill cuttings to the surface but also as a means of providing hydraulic
horsepower for downhole tools. Lifting and transporting of drill cuttings to the surface lies on, but not solely on the
rheological properties of the drilling mud in used but also on the mud pump pressure exerted at the surface. The pump
pressure which provides the circulating density of the mud is such that it is equivalent to the formation pressure.
Above this pressure, the formation tends to fracture and formation fracturing is not a good development during any
drilling operation. Hematite has been used as an additive to mitigate against formation pressures successfully,
especially when combined with the conventional weighting agent such as barite, calcium carbonate, etc. Barite (with
specific gravity between 4.2 – 4.8 g/cm
3
) is the most popular of the weighting agents due to its ecofriendly nature. It
has been used severally to control the mud weight of drilling mud during weighting up process. This weighting up
process usually have significant effect on the equivalent circulating density (ECD) which in turn affect the cuttings
removal process, hence poor hole cleaning and resultant increase in torque. Besides the increase in demand of barite
and its global reserves reduction, there is need to look at other alternatives such as hematite, ilmenite, calcite, etc.
Hematite with a specific gravity of 4.7 g/cm is a good weighting agent in water base mud because it provides high
value of mud density with low solid content when compared with equivalent volume of barite.