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Principles of Drilling Fluids
钻井液工艺原理
Chapter 9
Solids control
固相控制
Prof. Dr. Xiuhua Zheng
E-mail: [email protected]
Exploration Dept. School of Engineering and Technology, China University of Geosciences(Beijing)
中国地质大学(北京)工程技术学院勘查教研室
Quiz for Glossary of §8
1. Diagenesis
2. Water sensitive
3. Sloughing/collapse
4. Cation Exchange Capacity
5. Encapsulator
6. Lubricants
7. Penetration rate
8. Loss Circulation
9. Sticking
10. Borehole stability
Drilling Fluids
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Solids control
1. 成岩作用
2. 水敏性
3. 坍塌
4. 阳离子交换容量
5. 包被剂
6. 润滑剂
7. 机械钻速
8. 井漏
9. 卡钻
10. 井壁稳定
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Glossary of §9
1. 固相含量
2. 固控
3. 振动筛
4. 除砂器
5. 除泥器
6. 清洁器
7. 筛布
8. 水力旋流器
9. 离心机
10.有用固相
1. Solid contents
2. Solid Control
3. Shale shaker
4. Desander
5. Desilter
6. Mud cleaner
7. Screen cloth
8. Hydrocyclones
9. Centrifuges
10. Usefur solid
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Contents
1. Solid contained in drilling fluid(钻井液中的固
相)
2. Contents and purposes of solid control(固
控的内容和目的) Drilling String Sticking
卡钻
3. Solid control equipment(固控设备)
4. Arrangement of Solids Control Equipment
System(固控设备体系组合的原则)
5. Evaluation of Efficiency of Solids Control
Equipemnt(固控设备效率评价)
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1. Solid contained in drilling fluid
(钻井液中的固相)
Solids contained in drilling fluid include bentonite, weighting
materials and drilled solids (drilled cuttings of formation rocks
or formation detritus derived from sloughing or collapse).
1.1 Bentonite
Bentonite is strongly hydratable and swelling active clays and its
chemical composition is water-containing silicates-aluminates that can be
dispersed into water as very fine colloidal particles (<2 μm) there-with form
a stable colloidal suspension. Particle size distribution of bentonite in fresh
water can be seen in Fig.1-1.
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1.1 Bentonite
Fig. 1-1 Particle size distribution of a bentonite in fresh water
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1.1 Bentonite
Bentonite is a useful and important solid component of
drilling fluid because it can provide the drilling fluid with the
following necessary behaviors:
1.Rheological properties as PV, YP and gel strengths.
2.Filtration, mud cake building and borehole wall
strengthening.
3.Carrying and suspension capacity of drilled cuttings
and weighting materials.
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1.1 Bentonite
Cation Exchange Capacity (CEC) is a parameter that represents the
activity of the bentonite. The higher the CEC value is, the greater the
bentonite ability to build up viscosity at a given concentration. The CEC
values of different clay minerals are listed below in Table 1-1.
Table 1-1 CEC of Different Clay Minerals
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1.1 Bentonite
The bentonite of higher CEC is preferable to be applied because it
may provide the drilling fluid with upgraded behaviors and performance
at its minimum content. Recommended range of properties and low
density solids of weighted water base mud is illustrated in Fig. 1-2 and
1-3.
Fig. 1-2
Plastic
viscosity,
yield point
and
Methylene
Blue Test
(MBT)
range for
water-base
muds
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1.1 Bentonite
Fig. 1-3 Solids range for barite weighted water-base muds
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1.1 Bentonite
The yield curve of different clays can be seen in Fig. 1-4.
Fig. 9-4
Typical clay
yield curve
A good salt
clay in salt
water
approximates
the bentonite
yield curve in
fresh water
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1.2 Weighting Materials
A good weighting material should meet the following requirements:
1.Higher density.
2.Chemically inactive or inert.
3.Low hardness and abrasiveness.
4.Safe to labor health.
Table 1-2-1 API Specifications of Barite
Requirements
Standard
Density
4.20 g/cm3,minimum
Water soluble earth metal,as calcium
250 mg/kg, maximum
Residue greater then 75 μm
Maximum mass fraction 3.0%
Particles smaller than 6 μm in equivalent Maximum mass fraction 30%
spherical diameter
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1.3 Drilled Solids
Drilled solids are cuttings of bit broken formation rocks or detritus derived
from formation sloughing or collapse and intruded into drilling fluid in drilling
process. They are predominantly clays, shale, quarts, feldspar as well as
limestone, dolomites etc. The tolerable content of drilled solids in drilling fluid
is less than 6 % (V/V).
Fig. 1-3-1 Particle size distribution of a shale in a native
mud
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1.3 Drilled Solids
The physical and chemical characteristics of solids
contained in drilling fluid are listed in Table 1-3-1.
Table 1-3-1 Physical and Chemical Characteristics of Solids Contained in Drilling
Fluid
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2.Contents and purposes of solid control(固
控的内容和目的)
2.1 Contents of Solids Control
1. Elimination of drilled solids.
2.Elimination of excessive bentonite content and colloid
particles.
3.Recovery of barite.
4.Recovery of chemical additives and water.
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2.2 Purposes and Significance of Solids
Control
• Maintain adequate mud rheological and filtration properties.
• Improve lubricity and reduce abrasiveness and friction of mud and
mud cake.
• Reduce drilling torque and drag.
• Reduce frequency of differential sticking and logging troubles.
• Reduce surge and swab pressure.
• Increase penetration rate and prolong bit footage and life.
• Reduce water, barite and chemical additives consumption.
• Smooth casing running and improve cementing quality.
• Obtain gauge hole and enhance borehole stability.
• Reduce wear of pump and equipment parts.
• Control mud weight and mitigate formation damage.
• Reduce mud drainage and haul-off.
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3. Solid control equipment(固控设备)
3.1 Shale Shakers(振动筛)
A. Capacity and efficiency of shale shaker
The volume of fluid processed per unit of time by a shale shaker
depends on the following factors:
a. Type of screen motion.
b. Vibrating amplitude of the screen.
c. Vibrating frequency of the screen.
d. G-force
e. Mesh and weaving type of screen cloth.
f. Drilling fluid properties such as density, PV, YP and gel strengths.
g. Load of solid on the screen
B. Screen cloth（筛布）
The specifications of common oilfield screens can be seen in Table 31-1 and the equivalent screens used by varied firms are listed in Table
3-1-2
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3.1 Shale Shakers(振动筛)
Table 3-1-1
API Screen
Designation
Chart
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3.1 Shale Shakers(振动筛)
Table 3-1-2 Screens of Shale Shakers of Different Firms
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3.1 Shale Shakers(振动筛)
C. Shale shaker applications.
a). Determination of screen mesh
b). a finest screen as 200 mesh can be applied when Gumble shalelike formations are drilled, a PDC bit is applied or ROP is low in a deep
well.
c). Number of shakers applied
d). Arrangement of shakers.
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3.2 Hydrocyclones(水力旋流器)
A. Classification.
Hydrocyclones are divided in two categories ( desanders
and desilters). The specifications of hydrocyclones are
shown in Table 3-2-1.
Table 3-2-1 Specifications of
Desanders and Desilters
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3.2 Hydrocyclones(水力旋流器)
B. Application of desanders and desilters.
a). The cut point of 10 in or 12 in desanders is 40-45 and that of 4 in
and 5 in desilters 20-5 .
b). Number of hydrocyclones: the number of &sanders arranged in a
set for a rig is determined in the way that the capacity processed by the
defined number of hydrocyclones of a set of desanders must be equal
to 125 % of the maximum rig circulating rate or more.
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3.2 Hydrocyclones(水力旋流器)
C.Factors influencing hydrocyclone performance.
1.Mud density.
2.Solid content of the underflow of the preceding equipment or solid
3.content of the mud that gets into the inlet of this unit.
4.Mud viscosity.
5.Feed pressure.
6.Feed flow rate.
7.Apex size.
8.Cyclone performance.
A sketch of hydrocyclone functioning states is shown in Fig.3-2-1.
The performance curves of different size hydrocyclones is shown in Fig.
3-2-2.
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3.2 Hydrocyclones(水力旋流器)
Fig. 3-2-1 Hydrocyclone functioning states (a) ConeSpray underflow discharge
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Fig. 3-2-2 Hydrocyclone functioning states (b)
Rope underflow dischargeF
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3.2 Hydrocyclones(水力旋流器)
As Fig.3-2-3 shows, the 12 in hydrocyclone removes about 50 % of 44
μm solid particles contained in the fluid that enters into the feed inlet so
as 44μm is called the CUT POINT, of the 12 in cyclone.
Fig. 3-2-3 Typical cyclone perfomance
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3.2 Hydrocyclones(水力旋流器)
In Table 3-2-2, the recommended feed pressures of hydrocyclones
of some manufacturers are listed.
Table 3-2-2 Recommended Hydrocyclone Feed Head Requirements
(All Pressures Based on 9 lb/gal Mud)
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3.3 Mud Cleaner(清洁器)
• A mud cleaner is introduced for treatment of weighted
mud instead of desilters with the purpose of avoiding waste
of barite. A mud cleaner is composed of a set of desilters
(usually 4 in hydrocyclones) mounted above a fine mesh
screen shaker (commonly 120-200 mesh, 117- 74μm) so
that the underflow of the desilters can pass through the fine
screen that discharges the solids larger than 74μm into
reserve pit and lets its liquid containing a good part of
barite pass through the screen and be conveyed into
circulating system.
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3.4 Centrifuges(离心机)
A. Functions of centrifuges.
Centrifuges are used to remove very fine solid particles (small down
to 10 or 7 μm). Since these fine particles affect mud rheological
parameters in a much greater degree than the coarser particles
therefore centrifuges can effectively control mud rheological properties
and penetration rate in a favorable range by removing extra-fine
particles. Besides this function, centrifuges are also applied for
recovering barite while discarding fine particles from weighted mud.
Centrifuges can treat only a part of the mud circulating rate (usually
10-20 % ) and they run usually with water dilution (20 -5 % ) for more
efficient separation.
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3.4 Centrifuges(离心机)
B. Types of centrifuges.
a) Decanting centrifuge:
The decanting centrifuge is composed of a rotating bowl and a
screw conveyor inside the bowl. There are three types of decanting
centrifuges: Barite Recovery Centrifuge, High Volume Centrifuge and
High Speed Centrifuge(Table 3-4-1 )
Table 3-4-1 Operational Parameters of Varied Decanting Centrifuges
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3.4 Centrifuges(离心机)
b).Rotary Mud Separator Centrifuge (RMS):
The RMS centrifuge is composed of a stationary case and a
perforated cylinder that revolves concentrically within the case at a
defined speed.
RIMS centrifuge has greater handling capacity and coarser discard
than decanting centrifuge and its cut point depends on the geometry
and mechanical design of the unit. The sketches of decanting
centrifuge and RMS centrifuge can be seen in the following figures
(Fig.3-4-1 and Fig. 3-4-2).
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3.4 Centrifuges(离心机)
Fig.3-4-2 RMS centrifuge
1 --Stationary Case and
Underflow, 2 --Rotor (Rotating
Perforated Cylinder), 3 --Rotor
Shaft--Perforated
Fig. 3-4-1 Solid Bowl
Decanting Centrifuge
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3.4 Centrifuges(离心机)
c).Centrifuge applications.
Centrifuge can be applied in the following modes:
1. Recovering barite and removing ultra-fine and colloidal size solids
in weighted mud with a single Barite Recovery Centrifuge as the fig
3-4-3 follow:
Fig. 3-4-3 Recovering barite with a single Barite Recovery Centrifuge
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3.4 Centrifuges(离心机)
2. Dual centrifuging for recovering barite and removing ultra- fine
and colloidal size solids in weighted mud (Barite Recovery CentrifugeHigh Speed Centrifuge Combination). The cleaned liquid separated by
the High Speed Centrifuge can also b~ used to dilute the feed mud of
the first unit--the Barite Recovery Centrifuge or dilute the recovered
barite (Fig.3-4-4).
Fig. 3-4-4 Dual centrifuging for barite recovery and removing ultra-fine particles
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3.4 Centrifuges(离心机)
3. Secondary recovery of hydrocyclone discharge: The solids
separated in the underflow by the centrifuge are discarded to the
reserve pit and the cleaned liquid is returned back in the mud
circulating system or to the feed inlet of a High Speed Centrifuge for
further cleaning (Fig.3-4-5).
Fig. 3-4-5 Secondary recovery of hydrocyclone discharge with centrifuge
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3.4 Centrifuges(离心机)
4. Water recovery from reserve pit. The mud from the reserve pit is
fed to a High Speed Centrifuge for water recovery. The solids
separated by the unit are discarded to a dump pit and the cleaned
liquid is reverted to the circulating mud system or collected into a tank
for further use (Fig. 3-4-6).
Fig. 3-4-6 Water recovery from reserve pit with centrifuge
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4. Arrangement of Solids Control Equipment
System(固控设备体系组合的原则)
4.1 Principles of Composing a Solids Control Equipment System
A. Two or three shale shakers can be equipped in a drilling rig.
B. The number and operational behaviors of the desanders should
be carefully selected and adjusted so that they can clean completely
the larger particles that are out of the processing range of the
downstream desilters or mud cleaner.
C. The capacity of centrifuges is small that represents only a part of
the circulating mud. In order to make them work efficiently, they run
usually with water dilution of the mud at their feed inlet all the time.
A solids control equipment system, the separating capacity and the
cut point of its components are shown in Fig. 4-1-1.
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4.1 Principles of Composing a Solids Control
Equipment System
Fig.4-1-1 Minimum particle cut size and
capacity of different solid control equipment
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D. Because desanders and desilters may discard barite, so they
cannot be run when a weighted mud is applied for the purpose of
avoiding barite loss.
4.2 Commonly Used Solids Control Equipment Systems
A. Conventional solid control equipment system for un-weighted mud
(Fig. 4-2-1).
B. Conventional solid control equipment system for weighted
mud(Fig. 4-2-2).
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4.2 Commonly Used Solids Control
Equipment Systems
Fig. 4-2-1 Arrangement of solid control equipment
for unweighted mud
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4.2 Commonly Used Solids Control
Equipment Systems
Fig. 4-2-2 Arrangement of solid control
equipment for weighted mud
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5. Evaluation of Efficiency of Solids Control
Equipemnt(固控设备效率评价)
5.1 Calculation of Solids Separation Efficiency of One Unit from Solid
Control Equipment System
A. Calculation of low density solids separation efficiency
of one unit:
ER  LS
VU  LS  QU

VLS  Q
9-1
B .Calculation of barite separation efficiency of one unit:
ER  B
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VU  B  QU

VB  Q
Solids control
9-2
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Where:
• ER-LS -Low density solids separation efficiency of one unit from solid control
equipment system, %,
• VU-LS--Low density solid content in the underflow of one unit from solid control
equipment system (can be determined with retort), %,
• QU--Underflow volumetric rate of one unit from solid control equipment system
(can be determined using stop watch pail method), gal/rain,
• VLS--Low density solid content in the inlet of one unit from solid control
equipment system (can be determined with retort), %,
• Q--Inlet flow volumetric rate of one unit from solid control equipment system
(can be read from flow-rate meter), gal/rain,
• ER-B--Barite separation efficiency of one unit from solid control equipment
system, %,
• VU-B--Barite content in the underflow of one unit from solid control equipment
system (can be determined with re tort), %,
• VB --Barite content in the inlet of one unit from solid control equipment system
(can be determined with retort), %.
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5.2 Calculation of Drilled Solids Elimination
Efficiency
• Calculation of cuttings removing efficiency of the whole
solid control equipment system:
ETR  LS
V1U  LS  Q1U  V2U  LS  Q2U  V3U  LS  Q3U  ...

V TLS QT
9-3
Where：
ETR-LS--Cuttings removing efficiency of the whole solid control equipment
system, %,
V1U-LS V2U-LS V3U-LS…… -Low density solid content in the underflow of one
unit from solid control equipment system, %.
Q1U ,Q2U,Q3U … --Underflow rate volumetric of one unit from solid control
equipment system, gal/rain。
VTLS --Low density solid content of mud at the well flowline (before shakers),
%,
QT --Volumetric flow rate at well flowline (before shakers), gal/min.
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Discussion
• How does the solid content affect the
drilling and how control the solid
content?
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