Theory and Technology of Drilling Engineering

Fundamental concepts related on subsurface pressures are firstly introduced, including hydrostatic pressure, in situ stress, formation pore pressure, and formation fracture pressure. Based on them, the origin of abnormal pressures is analyzed. After that, prediction and detection of abnormal formation pore pressures, formation fracture pressure, and formation collapse pressure are discussed in detail. In the second section, the rock engineering mechanical characteristics are presented with respect to uniaxial strengths and triaxial strengths, rock brittleness, rock hardness, rock drillability, rock abrasiveness. Finally, the influencing factors of confining pressure on rock mechanical properties are analyzed.

This chapter discusses the components and functions of a drilling rig and drilling tools. A drilling rig usually has six necessary subsystems classified as hoisting system, rotary system, circulating system, well control system, power and transmission system, and monitoring systems. Drilling tools are used to describe drill strings and drill bits for rock breakage in a wellbore. A drill string usually consists of kelly, drill pipes, drill collars, and other tools such as stabilizers and reamers, which are included in the drill string just above the drill bit.

The commonly used drilling fluids and their functions and properties are briefly introduced in this chapter. The term of “drilling fluids” generally refers to all operational fluids that are used in the circulation during drilling. It is also named as drilling muds or simply muds. Drilling fluids can be in forms of either liquid or air. That is why it is termed as “drilling fluids” instead of “drilling liquids.” The importance of muds to drilling activities is similar as that of blood to human body. No drilling operation can proceed without using muds. Use of proper drilling fluids has a direct impact on the drilling progress and the associated drilling cost. The performance of drilling fluids is one of the key factors to the success of drilling operation.

Relationships between drilling parameters of weight on bit, rotary speed, tooth and bearing wear, hydraulic power, and rate of penetration (ROP) as well as drilling bit wear are first analyzed. After that, the method of optimizing mechanical drilling parameters is presented. Finally, the method of optimizing hydraulic parameters is introduced in terms of maximum hydraulic power and jet impact force based on drill bit flow analysis and frictional pressure loss evaluation.

Directional drilling technology is one of the most important drilling technologies in the field of oil exploration and development in the world today. It is a drilling technology that makes the drill bit reach the predetermined target underground by effectively controlling the wellpath with special downhole tools, measuring instruments and technologies. In this chapter we will discuss: the applications of directional drilling, the basic parameters of wellpath, wellpath measurement and calculation, the cause of well deviation and the deviation control technology during drilling a vertical well, the design method of well trajectory, calculations for azimuth correction run, and orientation methods of deflection tools.

Balanced pressure drilling is an important technology developed in the 1960s. It plays an important role in improving rate of penetration, reducing drilling costs, protecting reservoirs and prolonging the life of wells. This chapter firstly introduces the basic concept of pressure control in oil and gas well drilling and the balance relationship of the wellbore pressure system. Then it introduces the invasion and detection methods of formation fluids and common well control equipment. After that shut-in procedure, the law of wellbore pressure change and its control method in the process of kick and well killing methods are introduced in detail. Finally, current controlled pressure drilling technologies are described.

This chapter mainly introduces casing program design, casing strength design, cementing technologies, and well completion technologies. Casing program is the basis of drilling engineering which is to determine the casing levels, setting depth, top of cement, match of casing sizes, and hole section sizes. Casing strength design is mainly composed of the calculation method of external loading of casing, casing strength under combined external loadings and the conventional design method with safety factors for casing strings. The cementing technology includes types of oil well cement and additives, process of cementing, measures to improve displacement efficiency of cementing, weight loss of cement slurry and oil, gas and water channeling during wait on cement. The definition and application scope of perforation completion, open-hole completion, slotted liner completion, and gravel filling completion are introduced in completion technologies.

This chapter introduces the procedures of handling some complicated downhole conditions and accidents, coring operations, and sidetrack drilling technologies. Classification, causes, prevention and handling of complicated downhole conditions, and accidents are described in detail. Furthermore, tools for fishing broken drill string, falling objects accidents, and core drilling are introduced. The main factors affecting core recovery and the measures to improve core recovery are summarized. Different types of sidetrack drilling methods, tools, and processes are presented.