THE EFFECTS OF CONTAMINANTS ON THE FLOW OR RHEOLOGICAL PROPERTIES OF OIL BASED MUD

CHAPTER ONE
INTRODUCTION
 
1.1     Background of Study
Drilling for oil and gas with a drilling mud began many years ago in the 18th century. The first reported use of a drilling fluid was noted in France in 1845, when water was pumped down a hollow boring rod, while drilling water wells to bring the cuttings from the bottom of the well to the surface. (Ikeh, 2014)
 
Through the 1920's Iron oxide and Barium Sulphate (Barite) was used to increase the density of the drilling mud, thus preventing entry of the formation fluid into the borehole. The use of bentonite in 1930's to suspend Barite formed the basis for today's large commercial drilling mud industry. (Evabeta, 2004)
 
The term "drilling fluid" includes air, gas, water and mud or could either be a combination of two or all the above. The common type of fluid most often used in mud suspension of solid clay is a liquid and emulsion mud (suspension of solid and droplets of liquid). The drilling fluid is a term that comprises all the components of clay and additives suspensions used to effect the removal of rock cuttings from the subsurface (bottom hole) to the surface while drilling.
 
Thus, in other to enhance the drilling operation, the selected drilling mud must perform certain functions to avoid delay in operation and occurrence of associated drilling problems. Some of these functions are highlight below.
 
1.1.1  Functions of drilling fluids
 
  IV.            Suspend cuttings and weighting material when circulation is interrupted