The formulation of drilling fluid is one of the most important aspects in drilling engineering. This is because the drilling fluid is capable of lubricating and cooling the drill bit and drill string as well as carrying cuttings out of the borehole. All of these functions require appropriate viscosity of drilling fluid to facilitate pumping, circulate the cuttings, and transfer them to the surface.

2.  In the course of drilling an oil or gas
well by means of rotary drilling
tools, a so called ( Drilling mud ) is
circulated downwardly through the
hollow drill stem and bit to the
bottom of borehole and then
upwardly through the surface
through the annular space between
the drill stem and the interior of the
borehole.

3. During the drilling process, drilling mud
is applied to achieve specific
functional :
 Cool and lubricate the bit and drill
string.
 Transport cuttings to the surface.
 Suspend drill cuttings in the annulus
when circulation is stopped.
 Support the walls of the borehole.
 Stabilize the borehole.

4. This drilling mud system in which water is the continuous phase,
also; this is the most common drilling mud used in oil drilling.
The most common mud used in the type is bentonite due to; its
mixed friendly with water and allow mud additives to
perform efficiently well. Beyond that, it is cheap.
A number of additives are used to alter the mud properties to
fulfill all of the requirements of water-based drilling mud.
Both naturally occurring and synthetic polymers have been
widely used. Among them, chemically modified biopolymer
are probably one of the most extensively studied due to their
low cost, lack of toxicity (Zhang, Tan & Li, 2001).

7. Viscosifying agentGelling agent
pH controlling agentRust retardant
agent
Thermally stable up to 200 °C (16 hrs) with 0.5 % w/w

9. Noteworthy, most of the drilling mud additives are alkaline in
pH which requires to be adjusted to desired pH range via pH
controlling agent. Interestingly, lignin graft copolymer (LGC)
which is a modified bio-polymer has rheological controlling
property in tandem with an acidic character that may minimize
the use of pH controlling agents. Hence, the present study
evaluates the pH controlling ability of LGC.

10. Types of Mud T (oC) pH
Base Mud + 0.3% LGC 27 10.49
Base Mud + 0.5% LGC 27 9.63
Base Mud + 0.7% LGC 27 7.45
Base Mud + 0.3% LGC 90 10.15
Base Mud + 0.5% LGC 90 76
Base Mud + 0.7% LGC 90 60

11. Types of mud
pH
Before After
Base mud + 0.5% LGC 9.65 9.25
Base mud + 0.5 % CMC 11.62 9.30
Base mud + 0.5 % Guar Gum 11.53 8.73
Base mud + 0.5 % Xanthane 11.62 8.64

12.  As the LGC concentration increases in the drilling mud samples, the pH value
decreases. This acidification affect of the LGC could be results from two causes.
First, the acidification effect might be due to the use of sulphuric acid during the
separation process of the Kraft lignin from the other wood components.
 The other cause might possibly be corresponding to the branched acrylic monomer
in the LGC structure and the present of functional groups such as hydroxyl,
carbonyl, and ester as illustrated in FTIR spectrum. That might give the acidic
character to LGC when it was used as a drilling mud additive.

13. Acrylic group

15.  LGC has been successfully synthesized by exploiting the waste of
palm oil industry via the polymeric technique.
 Among all LGC concentrations which have been evaluated, only
0.5% w/w of LGC maintained the pH of the water-based mud
within the desired pH range.
 From an experimental point of view, the use of 0.5 % LGC as
drilling mud additives is not required any additional additives pH
controlling agent (soda ash and acetic acid), thereby it may reduced
the cost of drilling operation and minimize the environmental
damage.