Drilling Fluids Functللبلبللبلباions.pptx

Fluids

1. DRILLING FLUID FUNCTIONS

2. DRILLING FLUID FUNCTIONS FUNCTIONS of Drilling Fluids In order to successfully drill any well, the drilling fluid is called upon to perform a number of diversified, and often conflicting, functions! These functions are all inter-related to some degree! They also are affected by, or may affect, other operational requirements! You cannot drill a well without a drilling fluid!

3. DRILLING FLUID FUNCTIONS Question :- Why is the drilling fluid so important ? Answer :- The significance of drilling fluid in terms of its impact on the success or failure of a drilling operation can be compared to the significance of the blood circulating in our bodies. Blood diseases can be terminal !

4. DRILLING FLUID FUNCTIONS Answer (cont) :- Equally, poor drilling fluid design & selection can be terminal to our drilling and completion operations. Cutting corners to save a few dollars on drilling fluid design and selection inevitably translates into: Poor drilling performance and therefore a very high cost drilling operation. Failure to deliver quality geological and reservoir data. Failure to optimise reservoir productivity. The drilling fluid is at the heart of a drilling operation

5. DRILLING FLUID FUNCTIONS

6. DRILLING FLUID FUNCTIONS Additional Functions To SUPPORT part of the weight of the drill string and the casing. To CONTROL corrosion. To SECURE maximum hole information. To COMPLY with environmental regulations. To POWER Downhole Motors and Turbines. To TRANSMIT information from Downhole measurement equipment to the surface with a pressure pulse.

7. DRILLING FLUID FUNCTIONS Efficiently Transport Cuttings to Surface One of the most important functions of a drilling fluid. Cuttings must also be transported to the surface and easily separated from the fluid by the shale shakers. The cuttings should also arrive at the surface intact.

8. DRILLING FLUID FUNCTIONS Efficiently Transport Cuttings To Surface Efficient removal is dependent upon a number of factors: Annular Velocity Slip Velocity Viscosity Density

9. DRILLING FLUID FUNCTIONS The Effects of Annular Velocity Annular Velocity is the rate at which the fluid moves upwards in the annulus. Dependent upon PUMP OUTPUT Dependent upon ANNULUS DIMENSIONS The Annular Velocity should always exceed the SLIP VELOCITY of the cuttings Consideration must be given to maintaining the correct FLOW PROFILE .

10. DRILLING FLUID FUNCTIONS The Effects Of Slip Velocity Slip Velocity is the rate at which the cutting tries to settle through the moving fluid! Dependent on: Size of cutting. Density of cutting. Shape of cutting. Flow properties of the fluid.

11. DRILLING FLUID FUNCTIONS The Effects of Viscosity Viscosity is the internal resistance of a fluid to flow. Viscosity has a considerable influence on the CARRYING CAPACITY of a drilling fluid. There are practical limitations on viscosity, especially in technically difficult wells.

12. DRILLING FLUID FUNCTIONS The most important hole cleaning parameter is the Annular Velocity (A.V.) Where possible the annular velocity should be 100 ft/min, higher in deviated holes. In large hole sections the A.V. can be as low as 20 ft/min. If the A.V. is insufficient to clean the hole the viscosity must be increased For top hole high viscosities must be used Cuttings removal is harder in deviated and horizontal holes as the vertical component of the mud is reduced. A.V.(ft/min) = Pump rate (bbls/min) Annular vol. (bbls/ft) Slip Velocity (ft/min) = Cuttings velocity - A.V. Annular velocity

13. DRILLING FLUID FUNCTIONS DRILLING FLUID FUNCTIONS To Suspend Cuttings The ability to suspend the cuttings when circulation is interrupted is a function of the fluid’s….. REVERSIBLE GEL STRUCTURE We call this GEL STRENGTH and it indicates the ability of a fluid to suspend solids, as well as the ease with which the gels can be broken. Liquids such as drilling fluids which have the property of thickening at low or zero shear rates and becoming less viscous at high shear rates, are said to be Thixotropic . This is attributed to attractive forces between particles forming weak structures.

14. DRILLING FLUID FUNCTIONS DRILLING FLUID FUNCTIONS Insufficient Gel Strength Will cause solids to settle, which can result in: Bridging off of the wellbore Stuck pipe Hole fill Reduction of hydrostatic pressure Worse in deviated and horizontal wells as distance solids have to settle is very small

15. DRILLING FLUID FUNCTIONS To Control Pressures – Prevent flow of formation fluids Formations are composed of solids of varying porosity and permeability. They may contain liquids, such as water, gas or oil. These liquids may be under considerable pressure due to the overburden pressure and tectonic forces.

16. DRILLING FLUID FUNCTIONS To Control Pressures The fluid MUST maintain control of these pressures through the HYDROSTATIC PRESSURE of the fluid column. The FLOW PROPERTIES must also be considered. Hydrostatic Pressure Hydrostatic pressure (psi) = Height (ft) X Density (ppg) X 0.052

17. DRILLING FLUID FUNCTIONS Balancing Pressures If the hydrostatic pressure does not balance the pore pressure the following may occur: Influxes of formation fluid into the wellbore Lost circulation Hole Instability Stuck pipe Hydrostatic Pressure (psi) = Height (ft) x Density (ppg) x 0.052 Pore Pressure

18. DRILLING FLUID FUNCTIONS The Effects of FLOW PROPERTIES on Pressure When a drilling fluid is circulated, the resistance to flow (viscosity) imparts a certain added pressure to the pressure imposed by the pumps. Using Rheological & Hydraulics Models , we can calculate the additional pressures on the formation and the wellbore. The total applied pressure must not exceed the failure pressure of the formation.

19. DRILLING FLUID FUNCTIONS Failure to Control Pressures Failure to control pressures may cause the following: Influxes of formation fluid into the wellbore Lost circulation Hole instability Stuck pipe More serious problem is a blowout.

20. DRILLING FLUID FUNCTIONS

21. DRILLING FLUID FUNCTIONS To Isolate Fluids From the Formation The hydrostatic pressure exerted by the fluid should exceed the pressure existing in the formation. Only sufficiently to control the formation liquids and pressures The FLUID LOSS should be controlled The fluid should lay down a thin, impermeable filter cake. Liquid from the drilling fluid should not enter the formation.

22. DRILLING FLUID FUNCTIONS The Filtrate Losses Filtrate Losses: The fluid should lay down a thin, impermeable FILTER CAKE on porous and permeable formations. This is monitored in two tests: API Filtration Analysis HTHP Filtration Analysis Filter Cake

23. DRILLING FLUID FUNCTIONS The Filter Cake Reduces flow of fluid into the formation Should be thin and flexible with low permeability Thick filter cake will: Reduce the effective hole diameter Increase the chance of differential sticking

24. DRILLING FLUID FUNCTIONS Whole Fluid Losses Also known as LOST CIRCULATION . Controlled with specialised additives and procedures. Add materials such as: Flakes Fibres Granules X Link Polymers

25. DRILLING FLUID FUNCTIONS To Cool and Lubricate As a well gets deeper, the GEOTHERMAL GRADIENT causes the temperature of both the formation and the drilling fluid to increase. In addition, formations become more compacted, more abrasive and more difficult to drill as the depth increases. FRICTION is also a contributing factor to increasing the temperature.

26. DRILLING FLUID FUNCTIONS The drilling fluid ABSORBS much of the heat that is generated and conducts it away from the formation. A vast amount of this heat is LOST on surface. Lubrication is achieved through the laying down of a FILTER CAKE , and the use of specially formulated additives, which will reduce friction. Extra lubrication may be required between the drill string and the casing or wellbore, especially in directional wells. Use of additives To Cool and Lubricate

27. DRILLING FLUID FUNCTIONS To Support The Drill String And Casing String The drilling fluid is naturally buoyant . The degree of buoyancy is proportional to the density of the fluid. Any increase in the fluid’s density also increases the buoyancy of the fluid. More important as depth increases.

28. DRILLING FLUID FUNCTIONS To Maximize The Rate Of Penetration Many drilling fluid properties have a direct influence upon the rate of penetration: Fluid viscosity : Must be able to remove cuttings Should be low at high shear rates. Solids : Must not create cushioning effect between bit teeth and formation Should be as low as possible. Density: Hydrostatic pressure differential must be minimized Should be as low as possible.

29. DRILLING FLUID FUNCTIONS To Control Corrosion & Corrosion leads to loss of

30. DRILLING FLUID FUNCTIONS The drilling fluid should be NON-CORROSIVE to drill string, casing and drilling equipment. Corrosion can lead to: Wash outs Twist offs Pump failure Surface leaks Specific additives are used to control highly corrosive and toxic gasses such as HYDROGEN SULPHIDE and CARBON DIOXIDE . To Control Corrosion

31. DRILLING FLUID FUNCTIONS To Protect The Formations Drilled All interactions between the formation and the drilling fluid should be minimized. Prevent damage to formations of interest: Formation swelling Washouts Damage to the reservoir will result in loss of production or the need for remedial treatment.

32. DRILLING FLUID FUNCTIONS To Secure Maximum Information About The Well One of the main purposes in drilling any well is to obtain the MAXIMUM amount of information about the formations and the fluids they contain. Drilling fluids should deliver cuttings and gasses to the surface in a form close to that when they were drilled. Allow accurate wireline logging to be carried out .

33. DRILLING FLUID FUNCTIONS To Comply With Environmental Regulations The drilling fluid must not pose a threat to the environment or to the people exposed to it. All products and materials are regulated by the government and are classified according to the hazard, or potential hazard, they pose. Environmental testing and analysis now comprise a major part of all new fluids developments.

34. DRILLING FLUID FUNCTIONS To Recap The functions of a Drilling Fluid are many and varied. They are inter-related. That those functions are achieved is essential to the successful operation of drilling a well. WITHOUT THE DRILLING FLUID - YOU DON’T DO ANY DRILLING!