BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
when affected by excessive crude volumes should be corrected with necessary weight material for
density and appropriate additives for adjusting viscosity to desired levels.
Crude oil is always associated with natural gas, a mixture of gases that can contain both
hydrocarbons and non-hydrocarbons. Methane is normally the principal hydrocarbon component
of natural gas with smaller amounts of the paraffin series present, with some detection of benzene
and several naphthenes. Natural gases can contain large amounts of carbon dioxide, nitrogen, and
hydrogen sulfide as non-hydrocarbon. In some cases, helium and mercaptans have been detected.
Nearly all natural gases contain water vapor from the connate or formation water.
Subsurface hydrocarbons can exist in the gaseous state under certain conditions of pressure and
temperature, but separate as a liquid at the surface. Such subsurface hydrocarbon gas existing as
surface hydrocarbon liquid is referred to as condensate. Sometimes, natural gas accumulations are
found in association with salt water rather than liquid hydrocarbon. Generally, the nonhydrocarbon
gases can present problems for the drilling fluid. Both carbon dioxide and hydrogen
sulfide are discussed in this chapter.
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 4-15