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你可能喜欢Development of ester-based drilling fluids for wellbore enhancement
Ismail Jassim, Lina
Development of ester-based drilling fluids for wellbore enhancement.
PhD thesis, Universiti Putra Malaysia.
1590KbAbstractEster-based drilling fluid has been accepted as an alternative to mineral oils in drilling applications and currently being usedin oil or gas wells exploration around the world. However, the ester has many deficiencies such as high kinematic viscosity andpoorthermal and oxidative stabilities whichlimit its ability to carry and transfer drilled solids under high pressure and high temperature wells. Thus, the main aim of the study is to overcome these limitations by developing the high performance ester-based drilling fluids for deep and ultradeep wells that operate under high pressure and high temperature conditions. The low pressure technology was applied in the synthesis of the ester to minimize ester hydrolysis and thermal instability issues during the drilling operation. The rapid ester synthesis involved the reaction between2- ethylhexanol and vegetable oil-based methyl esters C8-12 in the presence of sodium methoxide as the catalyst. In order to obtain the optimum synthesis conditions, a response surface methodology (RSM) was appraised based on the central composite design. The product with 77 wt. % 2-EH C12 ester content wasobtainedfrom both RSMmodel and experimental data. The 2-EH C12 ester exhibited properties similar to the commercial ester, i.e. kinematic viscosity of 5.2 mm2/sec at 40°C and 1.5 mm2/sec at 100°C, specific gravity of 0.854, 170°C flash point, and -7°C pour point. While the properties of 2-EH C8/10 ester base oil were 3.2 and 1.2 mm2/sec of kinematic viscosity at 40 and 100°C respectively, 80°C flash point, and -15°C of pour point. Various conventional, micro and nano-ester-based drilling formulations were prepared and characterized based on the API Recommended Practice 13B-2. Calcium carbonate (CaCO3) of 5 μm particles, commercial graphene (powder and platelets) and carbon nanosphere (produced in house) nanoparticles have been used as the rheology enhancer and fluid loss agent in geothermal drilling fluid formulation.The performances of 2-EH ester-based drilling fluids were assessed under different hot rolling temperatures (121, 135, 149, 177, 212 and 232oC) for 16 hours. The improvement in both thermal and hydrolytic stability of the synthesized 2-EH C8-12 esters may be due to the unique transesterification method using methyl ester route as opposed to the conventional fatty acids route.Furthermore,the addition of only 0.1wt% of graphene (powder type) to the formulation enhanced further the ester-based drilling fluid performances. The stability of the fluid to plug 10 μm of formation size was evidenced when only 8 ml of filtration and 775 mDarcy of permeability was obtained using (533.4/50.8 × 25.4/101.6) mm ceramic disc. In this study, simulation of conventional and nano-ester-based drilling fluids in eccentric, dual phase flow through horizontal well was performed with the help of three dimensional CFD, Fluent package. The simulation was successful and demonstrated the capabilityof 2-EH ester based drilling fluid to carry and transfer cutting particles of 3, 4.45 and 7 mm sizes in a highly eccentric annular flow of 0.8 eccentricities. The critical fluid velocity that demonstrated the fluid ability to carryand transport cuttings without cuttings bed was at 2.86 m/s. These results confirmed that 2-ethylhexyl ester-based drilling fluids have the potential to be commercialized and used in deep and ultra-deep wells without sagging, pipe sticking, and wellbore instability issues.Item Type:Thesis (PhD)Subject:Drilling mudsChairman Supervisor:Professor Robiah Yunus, PhDCall Number:ITMA 2015 9Faculty or Institute:ID Code:58001Deposited By:
Haridan Mohd Jais
Deposited On:02 Nov Last Modified:02 Nov Repository Staff Only:
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with a base URL of http://psasir.upm.edu.my/cgi/oai2
Best viewed using IE version 7.0 (and above) Mozilla Firefox version 3 (and above) with the resolution of 1024 x 768.[讨论]对inlet/outlet&vent边界的理解
其实大部分的进出口边界条件都好理解，最让人困惑的是Pressure inlet/outlet和 inlet/outlet
vent的区别。下面是我对inlet/outlet vent边界的理解：
Pressure inlet/outlet是界面上没有遮挡的进出口边界，需要定义进出口边界周围环境的压力。
而inlet/outlet
vent是界面上被均匀遮挡的进出口边界，如下图所示，除了需要定义边界周边环境的压力外，还需要定义压力损失系数。
我这样理解的根据是帮助文件里面介绍压力损失系数的一段话：参看下图
其中第一句提到“inlet
vent被认为是无限薄的（狭窄的），通过该边界的压降与动态压力水头成比例，该比例是用户根据经验提供的损失系数。”既然是“无限薄的（狭窄的）”的进出口边界，就很容易让人联想到百叶窗类型的通风口，气流通过这样的通风口时的确会产生压降。
当然，我不确定这样的理解就是正确的。还请有经验的网友指正。
**********************************************************************************************
以下是帮助文件理对进出口边界的概述的翻译。贴出来免得将来又得看英文原文。
FLUENT中的进出口边界选项如下：
1.Velocity inlet速度进口边界：用来定义进口的速度和其他参数
2.Pressure inlet压力进口边界：用来定义进口的总压和其他参数
3.Mass flow
inlet质量进口边界：用于定义可压缩流的进口质量流量，没有必要在不可压缩流动中使用质量流量入口边界，因为当密度不变时，确定了流体速度即可确定质量流量。像速度进口和压力进口一样，质量进口也需要定义一些其他的参数。
4.Pressure
outlet压力出口边界：用于定义出口的静压（和其他考虑到回流的参数），当迭代过程中出口存在回流时，采用压力出口边界可以取得更好的收敛性。
5.Pressure
far-field压力远场边界：用于定义一个无限远处的可压缩自由流(free-stream
flow),这个边界需要定义自由流马赫数（free-stream Mach
number）和其他静态参数。这个边界只可用于可压缩流。
6.Outflow边界：用于出口速度和压力事先不清楚的出口边界，适用于出口流动接近于完全发展流动（fully
flow），因为outflow边界假设边界处沿流动方向的各种物理量梯度为0（压力梯度除外）。这种边界不适用于可压缩流的计算。
& &注意以下情况不可使用outflow边界：
&a.当入口为Pressure inlet时，出口应选用Pressure
&b.当计算可压缩流动时
&c.当计算密度可变的非稳态流动时，即使采用的是不可压缩流模型也不能用outflow边界
&d.多相流模型不可用outflow边界，唯一例外是明渠模型（open
7.Inlet vent边界：用于定义入口的损失系数、入口周围环境的总压和温度.
8.Intake fan进气风扇边界：用于定义一个外部进气风扇，其压力突变量（pressure
jump）、流动方向、周围环境总压和温度需要被定义。
9.Outlet vent边界：用于定义出口的损失系数、入口周围环境的总压和温度.
10.Exhaust fan边界：用于定义一个外部排气风扇，其压力突变量（pressure
jump）、流动方向、周围环境总压和温度需要被定义。
The inlet and exit boundary condition options in ANSYS FLUENT
are as follows:
1.Velocity inlet boundary conditions are used to define the
velocity and scalar properties of the flow at inlet
boundaries.
2.Pressure inlet boundary conditions are used to define the
total pressure and other scalar quantities at flow inlets.
3.Mass flow inlet boundary conditions are used in compressible
flows to prescribe a mass flow rate at an inlet. It is not
necessary to use mass flow inlets in incompressible flows because
when density is constant, velocity inlet boundary conditions will
fix the mass flow. Like pressure and velocity inlets, other inlet
scalars are also prescribed.
4.Pressure outlet boundary conditions are used to define the
static pressure at flow outlets (and also other scalar variables,
in case of backflow). The use of a pressure outlet boundary
condition instead of an outflow condition often results in a better
rate of convergence when backflow occurs during iteration.
5.Pressure far-field boundary conditions are used to model a
free-stream compressible flow at infinity, with free-stream Mach
number and static conditions specified. This boundary type is
available only for compressible flows.
6.Outflow boundary conditions are used to model flow exits
where the details of the flow velocity and pressure are not known
prior to solution of the flow problem. They are appropriate where
the exit flow is close to a fully developed condition, as the
outflow boundary condition assumes a zero streamwise gradient for
all flow variables except pressure. They are not appropriate for
compressible flow calculations.
7.Inlet vent boundary conditions are used to model an inlet
vent with a specified loss coefficient, flow direction, and ambient
(inlet) total pressure and temperature.
8.Intake fan boundary conditions are used to model an external
intake fan with a specified pressure jump, flow direction, and
ambient (intake) total pressure and temperature.
9.Outlet vent boundary conditions are used to model an outlet
vent with a specified loss coefficient and ambient (discharge)
static pressure and temperature.
10.Exhaust fan boundary conditions are used to model an
external exhaust fan with a specified pressure jump and ambient
(discharge) static pressure.
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