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IDT intern report drilling fluid
Typology: Thesis
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This is to certify that Mr. Pritam Kumar pursuing Bachelor of Technology
in Chemical Engineering from “National Institute of Technology,
has submitted a copy of project report after successful completion of the
training. Mr. Pritam Kumar has been very sincere & dedicated to his work at R&D-II Laboratory, of DF (R&D) TG-IDT, ONGC Dehradun.
various R&D centres under ONGC Integrated Institutes Services (OIIS) catering to various E&P activities including research, engineering, management and safety needs.
ONGC through its 100% subsidiary ONGC Videsh Limited (OVL) has 39 projects spread over 16 countries with 09 Producing assets in 07 countries namely Sudan, Russia, Vietnam, Syria, Brazil, Columbia and Venezuela.
To be a Global leader in integrated energy business through sustainable growth, knowledge excellence and exemplary governance practices.
World class-
Dedicated to excellence by leveraging competitive advantages in R&D and technology with involved people. Imbibe high standards of business ethics and organizational values.
Abiding commitment to safety, health and environment to enrich quality of community life. Foster a culture of trust, openness and mutual concern to make working a Stimulating and challenging experience for our people. Strive for customer delight through quality products and services.
Integrated In Energy Business-
Focus on domestic and international oil and gas exploration and production business opportunities. Provide value linkages in other sectors of energy business. Create growth opportunities and maximize shareholder value.
Dominant Indian Leadership-
Retain dominant position in Indian petroleum sector and enhance India's energy availability.
Carbon Neutrality-
ONGC will continually strive to reduce Carbon dioxide emissions across its activity chain with the objective of achieving carbon neutrality.
Forum , the Netherlands, International Alliance for Well Control , the Netherlands, and also from International Association of Drilling Contractors , USA.
The infrastructure for applied R&D has been developed with the state-of-the-art equipment and machines to achieve qualitative experimental results. Focus of R&D is directed towards drilling technology, drilling fluid engineering and cementation and cementing materials to meet challenges of drilling industry. The technologists and scientists provide solutions to the down hole drilling problems, improving design of the systems and thereby contributing towards the development of excellent, efficient and cost effective operations.
In geotechnical engineering, drilling fluid is a fluid used to aid the drilling of boreholes into the earth. Often used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells. Liquid drilling fluid is often called drilling mud. The three main categories of drilling fluids are water-based muds (which can be dispersed and non-dispersed), non-aqueous muds, usually called oil-based mud, and gaseous drilling fluid, in which a wide range of gases can be used.
The main functions of drilling fluids include providing hydrostatic pressure to prevent formation fluids from entering into the well bore, keeping the drill bit cool and clean during drilling, carrying out drill cuttings, and suspending the drill cuttings while drilling is paused and when the drilling assembly is brought in and out of the hole. The drilling fluid used for a particular job is selected to avoid formation damage and to limit corrosion.
NOTE- “Drilling fluid is as important to a drilling well as blood is to a human body”
The key to making the rotary drilling system work is the ability to circulate a fluid continuously down through the drill pipe, out through the bit nozzles and back to the surface. The drilling fluid can be air, foam (a combination of air and liquid or a liquid. Liquid drilling fluids are commonly called drilling mud.
Data source: The cuttings that the drilling mud brings to the surface can tell the geologist the type of formation being drilled.
To wall the hole with impermeable filter cake. This will give a temporary support to the wall of the borehole from collapsing during drilling.
Preventing caving in of the formations.
Acting as a medium for settling out of cuttings in the surface pit.
A drilling fluid can be classified by the nature of its continuous fluid phase. There are three types of drilling fluids:
These are fluids where water is the continuous phase. The water may be fresh, brackish or seawater, whichever is most convenient and suitable to the system or is available. The following designations are normally used to define the classifications of water based drilling fluids:
Non-Inhibited means that the fluid contains no additives to inhibit hole problems.
Inhibited means that the fluid contains inhibiting ions such as chloride, potassium or calcium or a polymer which suppresses the breakdown of the clays by charge association and or encapsulation.
Dispersed means that thinners have been added to scatter chemically the bentonite (clay) and reactive drilled solids to prevent them from building viscosity.
Non-Dispersed means that the clay particles are free to find their own dispersed equilibrium in the water phase.
Non-dispersed-non-inhibited fluids do not contain inhibiting ions such as chloride (Cl-), calcium (Ca2+) or potassium (K+) in the continuous phase and do not utilize chemical thinners or dispersants to affect control of rheological properties.
Non-dispersed- inhibited fluids contain inhibiting ions in the continuous phase, however they do not utilize chemical thinners or dispersants.
Dispersed-non-inhibited fluids do not contain inhibiting ions in the continuous phase, but they do rely on thinners or dispersants such as phosphates, lignosulfonate or lignite to achieve control of the fluids' rheological properties.
3.3.2 OIL BASED DRILLING FLUIDS
An oil based mud system is one in which the continuous phase of a drilling fluid is oil. When water is added as the discontinuous phase then it is called an invert emulsion.
3.4.1 Specific Gravity:-
SIGNIFICANCE:
Counter-balance the formation pressure, Control the loss of mud in weak zones, Facilitate the effective mud removal/displacement.
Normally, specific gravity of mud is kept higher for facilitating the displacement of cuttings from deep. The specific gravity difference of 0.2 to 0.5 gm/cc is normally recommended between mud and formation pressure.
Fig1:-mud balance
3.4.2 Viscosity: It is defined as the internal resistance of fluid flow. There are 2 types of viscosity which are Funnel Viscosity and Plastic Viscosity.
(a) Funnel Viscosity : It is time, in seconds for one quart of mud to flow through a Marsh funnel which has a capacity of 946 cm3 (See Fig2). A quart of water exits the funnel in 26 seconds. This is not a true viscosity, but serves as a qualitative measure of how thick the mud sample is. The funnel viscosity is useful only for relative comparison.
Fig2:- Marsh Funnel
(b) Plastic Viscosity (PV) : A parameter of the Bingham plastic rheological model (See Fig4). PV is the slope of the shear stress-shear rate plot above the yield point (See Fig4). Viscometer is equipment to measure Plastic Viscosity (See Figure 2). Plastic Viscosity is derived from the 600 rpm reading minus the 300 rpm reading and PV is in centipoises (cp). A low PV indicates that the mud is capable of drilling rapidly because of the low viscosity of mud exiting at the bit. High PV is caused by a viscous base fluid and by excess colloidal solids. To lower PV, a reduction in solids content can be achieved by dilution.
There are many rheology models shown in Figure 3. Normally Bingham Plastic Model is used to describe mud properties as Plastic Viscosity and Yield Point (See Figure 4).
3.4.4 Effective viscosity:
Effective viscosity is defined as the viscosity of a Newtonian fluid that exhibits same shear stress at the same rate of shear.
Effective viscosity at the shear rate γ1 is given by,
μe 1 = (τ 1 - τ 0 ) / γ 1 + (τ 0 / γ 1 ) = μp + (τ 0 / γ 1 )
Effective viscosity thus comprises of two components: plastic viscosity and structural viscosity.
3.4.5 Structural viscosity:
Structural viscosity represents the resistance to shear caused by the tendency of the particles to build a structure.
3.4.6 Yield Point (YP):
Physical meaning is the resistance to initial flow, or the stress required starting fluid movement. The Bingham plastic fluid plots as a straight line on a shear-rate (x-axis) versus shear stress (y-axis) plot, in which YP is the zero-shear-rate intercept (PV is the slope of the line).
YP is used to evaluate the ability of mud to lift cuttings out of the annulus. A higher YP implies that drilling fluid has ability to carry cuttings better than a fluid of similar density but lower YP.
Yield Point (Y.P.) = θ 300 – P.V.
3.4.7 Gel Strength:
It is the ability of fluid to suspend fluid while mud is in static condition. Before testing gel strength, mud must be agitated for awhile at 300 rpm in order to prevent precipitation and
then let mud is in static condition for a certain limited time (10 seconds, 10 minutes or maybe 30 minutes) and then open the viscometer at 3 rpm and read the maximum reading value.
3.4.8 pH: This value tells the Alkalinity of drilling fluid. pH should be more than 7 to preventcorrosion.
The digital pH meter as shown is used to measure the pH very commonly in the laboratories. These meters give trouble free performance.
Sensor housing is designed to mount at by-pass line thereby providing convenient of sensor & housing.
Fig: pH meter
3.4.9 Lubricity and Lubricity Coefficient:
One of the function of the drilling fluid is to lubricate the drill string. The requirement for lubrication is especially critical in directional and crooked holes and in avoidance of wall sticking.
The lubrication for the metal surface is provided by a pressure resistant film that is produced as a result of the chemical reaction initiated by a high temperature generated from friction at the area of contact.
