PASSAGE TWENTYSEVEN
Diamond Bits
Diamonds used in oilfield bits are of natural origin and range from as small as 15 stones per carat to seven carats per stone in special applications. Diamonds are very abrasive resistant extremely high in compressive strength, are the hardest material known today, but are low in tensile strength and have high thermal capacity.
A diamond bit is usually composed of three parts: diamonds, matrix and shank. The diamonds are held in place by the matrix, which is bonded to the steel shank. The matrix is principally powdered tungsten carbide infiltrated with metal bonding material. The tungsten carbide is used for its abrasive, wear and erosion resistant properties. The shank of steel affords structural strength and makes a suitable means to attach to the drill string by threads.
The reason for using diamond bits is to drill less expensive and safer wells. The absence of bearings and other moving parts in diamond bits usually permits a bit life several times, or many times, longer than that of conventional roller- cutter- bits, and longer life eliminates one or more round trips through a given time on bottom and improves daily footage, thereby reducing drilling costs. Indirect savings are also achieved in diamond drilling by reducing the risks of gas kicks and lost circulation problems on round trips.
131. Which characteristic of the diamond is extremely high? (A ) A. compressive strength B. tensile strength C. operating techniques D. diamond drilling
132. What are the three parts of a diamond bit? (B ) A. single crystal, coated and carbonado B. diamonds, matrix and shank
C. surface condition, interior structure and external shape D. compressive, tensile and structural strength external shape
133. What can the shank of steel afford? (C ) A. tensile strength B. compressive strength C. structural strength D. pressive strength
134. What is the reason for using diamond bits? (A ) A. to drill less expensive B. to drill less expenditious C. to drill less economic D. to drill less experienced
135. According to the passage, what do diamond bits belong to? (B ) A. fishing tools B. drilling tools C. handling tools D. casing tools
PASSAGE TWENTYEIGHT
Circulating System for Drilling Fluids
One of the essential features of a rotary drilling system is its circulating system,
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commonly called the mud system. For the rotary drilling system to function, fluid must be circulated downward through the drill stem, around the bit, and upward in the annular space between the drill stem and the wall of the hole or the casing.
The principal purposes of circulation fluid are to: clean the bottom of the hole, cool the bit, flush cuttings from the hole, support the walls of the well so that they do not cave in and prevent the entry of formation fluid into the borehole.
The circulation fluid is usually a liquid, but it is sometimes air or gas. If the circulating fluid is a liquid, it is usually made up mostly of water, although occasionally oil is the major component. Both types of circulating fluids are called drilling mud, because that is what they appear to be. Nevertheless, some drilling muds are quite a bit more than just muds; literally scores of special chemical additives are put into then in order to achieve the purposes outlined earlier with the greatest efficiency. In perhaps 1 percent of all oil wells drilled, compressed air or natural gas is used as the circulating fluid instead of mud.
The components of a mud- circulating system in which a pump is used to force the drilling fluid through the swivel, into the drill stem, and back to the surface again, where it returns to mud tanks or pits.
The art of mud control has developed as rapidly as any phase of the drilling business. It is one of the most complex subjects the drilling crew has to deal with. Special clays are used to give body to the mud, and barite, a heavy mineral, is added to increase the mud weight. Chemicals are used to control the thickness, or viscosity, of the mud and to improve the ability of the solid particles in the mud to deposit a layer, or cake, on the wall of the hole. 136. Which sentence is not the main purpose of the drilling fluids? (D ) A. clean the bottom of the hole B. cooling the bit
C. flush cuttings from the hole D. cool the drilling stem
137. What should we use to control the viscosity of the mud? (C ) A. special clay B. barite C. chemicals D. immobile oil
138. What is the circulating system commonly called? (B ) A. the rotary system B. the mud system C. the essential feature D. the chemical system
139. What is the circulating fluid mostly made up of? (A ) A. water B. gas C. air D. oil
140. What is this passage mainly about? (C ) A. formation evaluation B. drilling techniques C. drilling fluid D. oil transmission
PASSAGE TWENTYNINE
Test of Drilling Fluid Density
Density is weight per unit of volume, once the density is determined, it may be expressed
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in any convenient unit——for example, in pounds per gallon(lb/gal), pounds per cubic foot (lb/cu ft), specific gravity, or in pressure gradient as pounds per square inch (psi) per 1,000 feet of mud in the hole.
The mud weight is usually tested by a balance. A mud balance consists of a supporting base, a cup, a lid, and a graduated arm carrying a sliding weight. A knife—edge on the arm rests on the supporting base. The procedure for measuring the density of the mud reads as follows.
1.Set up the instrument base so that it is approximately level. 2.Fill the clean, dry cup with the mud to be weighted.
3.Place the lid on the cup, and seat it firmly but slowly with a twisting motion. Be sure some mud runs out of the hole in the cup.
4.With the hole in the cup covered with a finger, wash or wipe all mud from the outside of the cup and arm.
5.Set the knife on the fulcrum, and move the sliding weight along the graduated arm until the cup and arm are balance.
6.Read the density of the mud at the left—hand edge of the sliding weight. Make corrections when a range extender is used.
7.Report the result to the nearest scale division in lb/gal, lb/cu ft, specific gravity, or psi/1000 ft of depth.
Wash the mud from the cup immediately after each use. It is absolutely essential that all parts of the mud balance be kept clean if accurate results are to be obtained.
141. A graduated arm carrying a sliding weight is one of the components of (A ) A. a mud balance B. the mud weight C. the unit D. the plant
142. Which is the second step in measuring the density of the mud? (D ) A. Set up the instrument base so that it is approximately level.
B. Place the lid on the cup, and seat it firmly but slowly with a twisting motion. C. Wash or wipe all mud from the outside of the cup and arm. D. Fill the clean, dry cup with the mud to be weighted.
143. What is the passage mainly about? (B ) A. test of drilling fluid viscosity B. test of drilling fluid density C. test of oil viscosity D. test of oil density
144. Which of the following is not the unit of density? (A ) A. pounds per gallon B. pounds per cubic foot C. pounds per cubic meter D. pounds per square foot
145. How many steps are there in measuring the density of the drilling fluid? (C ) A. one B. four C. seven D.nine
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PASSAGE THIRTY
Crew Qualifications
The qualifications and experience of drilling personnel are important ingredients in ensuring rig performance and safety.
A proper evaluation of a drilling contractor today should include wages paid versus competitors, number of hours worked per day, number of days off and even benefits like health insurance. All of these have an effect on the quality and ability of personnel to perform adequately.
Additionally, the amount of travel time for the crews should be investigated. If they are traveling a hours each way to work a 12—hour tour, then fatigue could have negative effect on safety.
Some crew are working at just above minimum wage levels, sometimes just to quality for unemployment benefits again. If rig utilization increases much more, many contractors maintain that drilling crew problems could become acute.
Ask if the contractor is using pickup crews or personnel that have worked together for years and know what to do in an emergency. A crew familiar with the rig will make fewer mistakes in an emergency and problem better.
Crew training has been neglected as well. Many toolpushers, drillers and floor hands on land rigs are no longer certified in well control techniques. Although it is not often required for most land rigs, certification is required by law in some circumstance. Clarify the drilling contractor’s policy on this and make sure each crew member clearly understands emergency procedures if he has not received certified well control training. Remember that some crew members may not have worked in months or had to shut a well in for several years.
Frequent safety meeting and safety award programs may seem insignificant on the surface, but experts maintain they contribute significantly to the bottom line. Ensure some type of safety program is ongoing to minimize the risks.
146. The important ingredients in ensuring rig performance and safety are (C ) A. specification and maintenance of equipment B. qualification and experience of the contractors
C. qualification and experience of the drilling personnel D. the training and certification of drillers
147. Which is not often required for most land rigs? (B ) A. the qualification of drilling
B. the qualification of well control techniques C. the qualification of performance D. the experience of emergency
148. What does well control technique mean? (B ) A. ways in control
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B. skills in controlling wells
C. methods in performing a well D. techniques in operation
149. Which word can explain the meaning of ―crew‖? (D ) A. toolphshers B. drillers
C. floor hands D. drilling personnel
150. What is the subject of this passage? (B ) A. crew management B. crew qualifications C. drilling procedure D. salary of crew members
PASSAGE THIRTYONE
Safety Ensures Operation
Drilling crews should be instructed to watch for early signs of a washout, such as subtle decreases of a pump pressure chart or slight stroke increases to avoid costly fishing jobs. Consider running a seating nipple just above the collars to check for pressure integrity.
Drill collars should be examined for visible cracks or severe corrosion before use. Connections should be inspected for cracks in the thread and stress relief areas of both the box and pin ends. Wall thickness should be verified against manufacturer’s specifications to prevent failures and problems.
Check the capacity, pressure and weight ratings of important components before they can cause problems in an emergency. The condition of the drill line should be double checked as well as the ton- mile records. Some contractors are stretching the life of the drill line to the extent that it can cause serious safety hazards.
Time taken to verify compression rating and maintenance records before drilling is a good investment when weighed against the costs associated with delays or even catastrophic failure.
151. Why should the drill collars be examined for visible cracks or severe corrosion before use? (C )
A. to make the workers do something B. to increase the drilling profit C. to avoid the costly fishing jobs
D. to ensure the flexibility of the drilling fluid
152. What must we check of the important components before they can cause problems in an emergency? (B ) A. compression ratings and condition B. maintenance condition
C. wall thickness and corrosion
D. capacity, pressure and weight ratings
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