Radiant energy – Geological testing or irradiation – Well testing apparatus and methods
Patent
1995-01-09
1996-05-21
Willis, Davis L.
Radiant energy
Geological testing or irradiation
Well testing apparatus and methods
378 45, G01N 2322, E21B 4900
Patent
active
055192149
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of analysing drilling fluids and is particularly useful for the determination of solids in drilling fluids and differentiation between the different types of these solids.
2. Description of the Related Art
During the drilling of an oil or gas well, large volumes of solids cuttings are generated by the drill bit. These solids are conveyed to the surface by means of circulating drilling fluids, often known as "mud", which are often complicated mixtures of water, oil, soluble and insoluble minerals, polymers, surfactants and salts. A large portion of the drill cuttings can usually be removed from the fluid by means of vibrating screens and other solids separators, so that after this cleaning process the fluid can be recirculated down the drill string. However, some of the drill cuttings are dispersed as very small particles, which cannot be removed by the solids separation process. The presence of these fines, often called "drilled solids" (DS), affects the functional properties of the fluid. Determination of the concentration of DS is particularly complicated by the presence of two other types of solids in the fluid, commercial clays and weighting material.
Commercial clays are added to the fluid for control of rheological and filtration properties. Usually, bentonite or other chemically treated clay minerals are added for this purpose. The total of commercial clays (CC) and DS is called "low gravity solids" (LGS).
Weighting materials are used to bring the fluid to the required density, necessary to contain underground formation fluids by hydrostatic pressure exerted by the mud column in the annulus. A common weighting material is powdered barite (barium sulfate). The concentration of weighting materials is known as "high gravity solids" (HGS).
It is important for effective control of the properties of the fluid to know the individual concentrations of all types of solids. In current well site technology LGS and HGS are not measured directly, but are calculated from the density and solids volume fraction of the drilling fluid, both of which can be measured. The principle of the calculation is that both properties are functions of the volume fractions of LGS and HGS. A simple form of these functions is assumed, and from the resulting set of two simultaneous equations with two unknowns one can readily solve LGS and HGS. This is usually done by direct calculation or by the use of charts which may allow for corrections if salts are present.
The total concentration of clays can conveniently be determined at the well site from their ability to absorb certain cationic dyes. This is the basis for the well-known methylene blue test, which provides a value known as "MBT value" for the concentration of chemically active clays. The larger part of these clays comes usually from the intentionally added commercial clays, the remainder is derived from clay minerals in the drilled solid fraction. If an average proportion of chemically active clays in the drilled solids is assumed, then it is possible to calculate DS and CC from LGS and MBT.
As mentioned, previously proposed techniques for the determination of individual solids concentrations relies on the direct measurement of density and solids volume fraction of the fluid. Density is measured with a "mud balance", a well-known rig site device. Solids volume fraction is measured by evaporation of a fluid sample of known volume in an electrically heated distillation apparatus, also well-known as the "mud retort". The liquid distillate is collected in a graduated receiver, and from the volume of distillate and the volume of the original fluid sample the volume fraction of total solids is calculated. Problems associated with the use of these two pieces of equipment are the possibility of an incorrect apparent density as determined by the mud balance because of the presence of gas in the fluid sample, and further, the fact that the mud retort suffers from errors caused by leaks in t
REFERENCES:
patent: 3848881 (1974-10-01), Barton, Jr. et al.
patent: 3858037 (1974-12-01), Moore et al.
patent: 4510573 (1985-04-01), Boyce et al.
Gilmour Alan
Houwen Otto
Sanders Mark
Hanig Richard
Kanak Wayne I.
Lee Peter Y.
Schlumberger Technology Corporation
Willis Davis L.
LandOfFree
Method for analysis of drilling fluids does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for analysis of drilling fluids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for analysis of drilling fluids will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2039614