George R. Gray

Introduction to Drilling Fluids

This chapter is a general introduction to the composition, functions, properties, and systems used to drill oil and gas wells. A description of the various levels of expertise, as defined by the API for a drilling fluid specialist are covered. The reasons for using a drilling fluid are given in the functions section, the two main properties to satisfy the functions being density to control pressures and viscosity for hole cleaning and suspension. The composition of drilling fluids is related to the base fluid used to formulate the fluid—water, nonaqueous, or pneumatic. The properties of the fluid, as tested by the drilling fluid specialist, are described. The properties tested are classified as controlling the mud weight, viscosity, fluid loss, and chemical reactivity. The selection of a drilling fluid is related to commonly used drilling fluids systems. A brief description of common solids control equipment is included.

Drilling Fluid Components

This chapter covers the types of drilling fluids and the additives used in those fluids. The products covered include weight materials, lubricants, viscosifiers, lost circulation materials, shale stabilizers, surfactants, emulsifiers, bacteria control, corrosion inhibitors, and their environmental aspects.

Clay Mineralogy and the Colloid Chemistry of Drilling Fluids

This chapter covers clay mineralogy and colloid chemistry. The origins of clay minerals, swelling mechanisms, and the chemistry of clays and clay gelation are covered. Also included are descriptions and uses of water-dispersible polymers in water-based drilling fluids.

Drilling Problems Related to Drilling Fluids

This chapter covers those drilling fluids issues that can cause delays in drilling the well. These issues can be very expensive and need to be eliminated or remediated as quickly as possible. These problems include stuck pipe, wellbore instability, slow drilling rates, excess torque and drag, lost circulation, high temperature additive degradation, and corrosion.

The Rheology of Drilling Fluids

This chapter covers the viscosity characteristics of drilling fluids based on their measured rheological properties. Various mathematical flow models are covered, including the Bingham plastic and power law equations. The application of rheological data for hydraulics calculations is also covered.

Water-Dispersible Polymers

This chapter covers the water-dispersible polymers used as additives in fresh and brine water drilling fluids. Each polymer type is discussed in detail as to its structure, manufacture, and temperature. The differences in polymer usage are covered, and emphasis is put on the type of poymer to use to adjust specific drilling fluid properties-bulk viscosity, low shear rate viscosity (LSRV), suspension, chemical reactivity, and fluid loss control.

Completion, Workover, Packer, and Reservoir Drilling Fluids

In Chapter 2, Introduction to Completion Fluids, the functions and composition of completion fluids, primarily brine waters, and additives, were covered. This chapter covers the operational aspects of various types of completion fluids. The first part is an explanation of formation damage from the drilling operation and the relative nature of cost versus value in drilling and completion fluids operations. The aspects of fluid selection are covered based on type of completion, primary verses workover, and remedial operations.

The Filtration Properties of Drilling Fluids

In this chapter, we discuss the principles of static and dynamic filtration, and the best means of correlating between them. Darcy’s Law is used to relate filtration theory to drilling fluid loss downhole. The importance of the filter cake is discussed, as well as good practices to minimize fluid loss by having the proper particle size distribution in the drilling fluid to give a low permeability cake. Particle size distribution is also discussed in relation to bridging formation openings.

Equipment and Procedures for Evaluating Drilling Fluid Performance

This chapter covers the equipment and procedures necessary to perform the API standard drilling fluid tests. It describes the procedures for determining drilling fluid data for mud weight (specific gravity), viscosity and rheological profiles, fluid loss, and the physical-chemical properties.

Drilling and Drilling Fluids Waste Management

This chapter covers drilling waste management including the impact of drilling fluids on waste management. The differences between water-based and nonaqueous drilling fluids are covered along with handling and disposal options for each fluid. The effect of drilled cuttings are covered in detail and disposal options, such as injection underground and onshore and offshore disposal techniques, are covered. Current environmental lab testing is included, such as biodegradation and toxicity protocols. The US Waste Regulation Bibliography is included.