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Drilling engineering

Drilling is the most expensive part of most projects. The drilling engineer is responsible for the well reaching its target safely, on time and within budget.

The lessons run from equipment and tools to the pressures in the well and control over it, then to casing the hole, fluids and hydraulics, trajectory and measurements while drilling.

35 / 35 topicsWhere to start: How a well is drilled: the process and the people involved

The rig and the drilling process

  1. 01How a well is drilled: the process and the people involvedThe rotary drilling rig, the stages of building a well from the conductor to completion, the roles of the operator, the drilling contractor and the service companies, the drilling programme and cuttings lag time. Basic
  2. 02Drilling time and costThe days-versus-depth curve and flat time; productive and non-productive time, invisible lost time, technical and commercial drilling speed; estimating a new well from analogues; the cost estimate (AFE) — time-dependent, depth-dependent and lump-sum costs, tangible and intangible, cost per metre; contingency from a risk register and the P90 cost; the learning curve in a series of wells; dry hole and completed well. Basic
  3. 03Drilling rig: power and hoisting systemsThe power drive — mechanical, diesel-electric with DC or AC, or from the grid — and the power and fuel required; the hoisting system: drawworks, crown block and travelling block, number of lines strung and block-and-tackle efficiency, tension in the fast line and dead line, line design factor, drawworks power and hoisting speed, derrick load and the load on its legs, rig classes under GOST 16293-89; line work in tonne-kilometres and the slip-and-cut programme — with calculations for a 4800 m string. Basic
  4. 04Rig circulating and rotary systemsThe path of the mud and the surface circulating system; triplex and duplex mud pumps, output per stroke and volumetric efficiency, liners and allowable pressure, the power limit, pulsation dampener and charge pump; strokes to the bit and “bottoms up”; the rotary table, kelly, swivel and top drive, rotary power; what is measured on the rig and how to read changes — with calculations for a 3000 m well. Basic

Drill string and bits

  1. 05Drill string: pipe, tool joints, drill collars and heavy-weight drill pipeWhat a drill string is made of: drill pipe (sizes, nominal weight, strength grades, length ranges), tool joints and their threads, heavy-weight pipe and drill collars — plain, spiral and non-magnetic — stabilizers, reamers, jars, shock subs and crossover subs, the kelly and the top drive; tensile and torsional strength of the pipe body, wear, inspection and the classes of used pipe. Basic
  2. 06Drill string designThe weight of the string in mud and the effective axial force, weight on bit and the neutral point, the length of drill collars and HWDP with a design factor, stability of compressed pipe in a deviated hole, tensile design from the bottom up with margin of overpull and crushing in the slips, drag and torque from the soft-string model; full calculations for a vertical and a directional well. Intermediate
  3. 07Drill bits: types and designHow a bit breaks rock — by indentation, shearing and abrasion; the design of roller-cone bits (cutting structure, cone offset, bearings and seals) and PDC bits (cutters, body, blades, back rake, profile, gauge); diamond, impregnated and hybrid bits; nozzles and junk slots; choosing the type of bit for the section in outline. Basic
  4. 08Bit selection and dull gradingIADC codes for roller-cone bits (series, type, bearing, feature letter) and for fixed-cutter bits (body, cutter density, cutter size, profile), the designation of roller-cone bits under GOST 20692-2003; rock strength beneath the bit under overbalance, choosing a bit from the section and offset-well records, revolutions per run; the eight positions of the IADC dull grading code — evaluation of PDC cutters and teeth, the two-thirds rule for gauge, feature codes, location and reason pulled — and what the wear says about the next run. Intermediate
  5. 09Bit performance and cost per metreRate of penetration and trip-averaged rate of penetration, cost per metre drilled and comparison of runs in offset wells; how the rate depends on weight, rotary speed, hole cleaning, overbalance and wear; the drill-off test — threshold and founder point; mechanical specific energy (MSE) and the bit friction coefficient; the Bourgoyne–Young model; the moment to pull the bit, from minimum cost per metre and from maximum trip-averaged rate — with calculations for a 4800 m well. Intermediate

Formation pressures and well control

  1. 10Pore pressure and overburden pressureHydrostatic pressure and gradients, normal and abnormal pore pressure, overburden pressure and effective stress, equivalent mud weight and the choice of mud weight. Basic
  2. 11Abnormal formation pressures: origin, prediction and recognitionWhere abnormally high and abnormally low formation pressures come from, how they are predicted before drilling and recognised while drilling, the d-exponent and pore pressure estimation by Eaton's method. Intermediate
  3. 12Fracture gradient and leak-off testingWhy rock fractures against its least stress, estimating fracture pressure before drilling, the leak-off test under the casing shoe (LOT, FIT), the allowable mud weight, MAASP and the choice of casing setting depths. Intermediate
  4. 13Well control: primary barrier and kick indicatorsPrimary and secondary well control, the causes of kicks — from insufficient mud weight to swabbing, failure to keep the hole full and lost circulation — direct and indirect indicators of a kick and the behaviour of gas in the wellbore. Basic
  5. 14Well kill methodsPressures in the drill pipe and annulus after the well is shut in, the density of the kill mud, initial and final circulating pressure, the driller's method, the wait-and-weight method, the volumetric method and bullheading. Intermediate
  6. 15Blowout prevention equipmentAnnular and ram preventers, the BOP stack and its hook-up, choke and kill lines, the choke manifold, the hydraulic control unit and the diverter; how the working pressure is chosen. Intermediate

Casing and cementing

  1. 16Casing: purpose, types, properties and standardsConductor, surface, intermediate and production casing strings, liners; the elements of a string, sizes, drift diameter, steel strength grades, threaded connections, rated pressures and loads, standards. Basic
  2. 17Wellheads and running casingThe wellhead casing arrangement: casing head, spools, slip and mandrel hangers, seals, pressure classes and testing; running the string: preparation, rig equipment, make-up by position, torque and the torque–turn plot, filling, hook load, running speed and pressure surges, landing, cutting off and installing the next spool — with an example on a 244.5 mm string. Intermediate
  3. 18Casing designDesign load cases for collapse and burst, net pressures with depth, design factors, graphical selection of sections, tension and biaxial loading — with a worked casing design. Advanced
  4. 19Oilwell cements and additivesPortland cement: clinker minerals and hydration; classes under API Spec 10A and types under GOST 1581; density, water–cement ratio and slurry yield from absolute volumes; thickening time, fluid loss, free water, strength and the tests for them; accelerators, retarders, lightweight and weighting additives, fluid-loss additives, dispersants, fillers, protection against gas migration; strength retrogression above 110 °C and silica — with a slurry design calculation. Intermediate
  5. 20Primary cementingThe objectives and methods of cementing, casing accessories and surface equipment, centralisation, displacement of the drilling fluid and spacers, volumes and materials, displacement pressures, plug bump (the “stop”) and the pressure differential across the float valve, free fall, waiting on cement and job monitoring; two-stage cementing, liners, the inner string, reverse circulation — with a complete job calculation for a 244.5 mm string. Intermediate
  6. 21Remedial cementing, cement plugs and cement evaluationHow cementing is checked: pressure testing, temperature logging, acoustic cement bond logging (amplitude, VDL, bond index), ultrasonic tools, microannulus and false readings; squeeze cementing — methods, equipment, the wellhead pressure limit; balanced cement plugs; abandonment and suspension of wells under Kazakhstan's rules — with calculations. Intermediate

Drilling fluids and hydraulics

  1. 22Drilling fluids: functions and propertiesThe functions of drilling fluid, density and weighting, rheology, filtration and filter cake, solids and chemistry, types of mud; the pressure of a fluid column in metric and oilfield units. Basic
  2. 23Field testing of drilling fluidsWhat is measured on the rig and how: density with an ordinary and a pressurised mud balance, funnel viscosity and viscometer readings, filtration in the standard test and at high pressure and temperature, the retort, sand content and the methylene blue test, pH, alkalinity, chlorides and hardness — with calculations from the instrument readings and recognition of contamination. Intermediate
  3. 24Water-based muds and clay chemistryThe structure of clay minerals, their charge and cation exchange capacity, the electrical double layer and the effect of salts, hydration and swelling, flocculation and deflocculation; bentonite and polymers, treatment against calcium, cement and other contaminants, inhibitive muds and choosing a mud for the section. Intermediate
  4. 25Oil-based mudsThe invert emulsion and its components — base fluid, brine, emulsifiers and wetting agents, organophilic clay, lime; the oil–water ratio from the retort and its adjustment, water-phase salinity and balanced activity, electrical stability and other tests, advantages and limitations, gas solubility and kick detection, handling of cuttings. Intermediate
  5. 26Solids control in drilling fluidsWhere drilled solids come from and why fine particles are more harmful than coarse ones; screening, settling by Stokes' law and dilution; shale shakers and API screen numbers, desanders and desilters, mud cleaners and centrifuges, the cut point and why hydrocyclones lose barite; flow schemes for unweighted, weighted and oil-based muds; the solids balance, the cost of dilution and solids-removal efficiency from actual data. Intermediate
  6. 27Drilling fluid rheology and flow regimesShear stress and shear rate, Newtonian and non-Newtonian fluids, the Bingham, power-law and Herschel–Bulkley models from viscometer readings, the Reynolds number and flow regimes, the effect of rheology on pressure losses and equivalent circulating density (ECD). Intermediate
  7. 28Circulating pressure lossesWhat makes up the standpipe pressure: surface lines, drill pipe and drill collars, bit nozzles and the annulus; laminar and turbulent losses for the Bingham and power-law models, regime boundaries and friction factors, the pressure drop across the bit, ECD by annular section against the lost-circulation pressure, the effect of flow rate and mud properties, pressure surges when running and pulling pipe. Advanced
  8. 29Bit hydraulics optimisationWhat the jets do at the bottom of the hole; bit hydraulic horsepower, hydraulic horsepower per unit area and jet impact force; the system pressure-loss exponent from two standpipe pressure readings; the optimum split of pump pressure by the criteria of power and impact force; flow-rate limits — pumps, cuttings transport, annular flow regime, ECD — and the graphical method; nozzle selection and the operating conditions towards the end of a run. Advanced

Directional drilling and measurements

  1. 30Directional wells: applications and profileWhy deviated wells are drilled; measured depth and true vertical depth, reference levels, departure and azimuth; kick-off point, build-up rate and radius of curvature; calculating build-and-hold and S-shaped profiles and what limits the choice of profile. Intermediate
  2. 31Deflection tools and downhole motorsHow to make the bit turn: the whipstock and sidetracking, positive displacement motors and the turbodrill, the bent sub and the steerable motor, sliding drilling and toolface, assemblies for building, holding and dropping angle, rotary steerable systems and what MWD and LWD give the driller. Intermediate
  3. 32Directional survey calculationsHow the position of the wellbore is found from measurements of inclination and azimuth: referring azimuths to a single north, the tangential, balanced tangential, average angle, radius of curvature and minimum curvature methods and their errors, dogleg and dogleg severity, departure, departure azimuth and displacement along the planned azimuth (vertical section). Advanced
  4. 33Survey instruments: magnetic, gyroscopic and inertialHow a survey tool finds inclination, azimuth and toolface from accelerometers and magnetometers; the Earth's magnetic field, declination on the date of the survey and grid convergence; interference from the steel of the string and the length of non-magnetic drill collars; checking a survey against the Earth's field; free gyros, gyrocompasses and inertial systems; errors, the ellipse of uncertainty and anti-collision. Intermediate
  5. 34Measurement while drillingThe make-up of an MWD/LWD system and the position of the sensors in the assembly; the survey taken at a connection and toolface while drilling; the mud-pulse channel — positive and negative pulses, continuous wave, attenuation and data rate; the electromagnetic channel and wired drill pipe; batteries and the turbine alternator; what each LWD measurement provides; geosteering; reliability and data verification. Intermediate

Offshore and subsea drilling

  1. 35Offshore and subsea drillingOffshore drilling units — islands, barges, platforms, jack-ups and semi-submersibles, drillships — and where the wellhead and preventers sit on each; building a subsea well from a jetted conductor to the hangers in the high-pressure wellhead housing; the riser and its tensioning; riser margin and the narrow pressure window in deep water, friction losses in the choke line; shallow gas; completion, suspension and abandonment; the northern Caspian — shallow water, ice, the Kashagan islands and the requirements for work in a nature-reserve zone. Intermediate

This section is growing: new topics are published after a technical review.