Hello mannu:
Deepwater drilling is defined as water depths of 1000 ft. or greater.
The chief problems encountered with selection of lubricant is “hole
cleaning”. Hole cleaning is necessary because the “cuttings” which
accumulate during the drilling process will mix with the lubricant
forming a cuttings bed gel.
Whether you use a water based mud (WBM) or a synthetic oil based mud
(SBM), depends on many variables. Adding glass beads to the mix will
also help in these environs.
There is a great deal of information on the Internet that specifically
address this topic. Some is free, some is not. If you belong to the
Society of Petroleum Engineers, you will find a wealth of free
information, if not they will charge per paper.
The Society of Petroleum Engineers (SPE) has a large library of oil
well specific papers on every aspect of the task. You need to register
to view the abstracts, and the full paper will cost about $10.00.
From SPE library:
Article # 74558
“The Effect of Drilling Fluid Rheological Properties on Hole Cleaning”
“Oil based and water based drilling fluids have been found to act
differently in respect to hole cleaning even though their viscosity
profiles may have been fairly equal. The different behavior is caused
by the different ways these drilling fluids are constructed. Oil based
drilling fluids are formulated using a continuous oil phase. The oil
based drilling fluids are viscosified by the addition of emulsified
water, typically in concentrations between 15 and 25% and by the
addition of organophilic clay. There is no contact between the
cuttings and the water when drilling with oil based drilling fluids. “
The following article will help you tremendously:
Article # 74546
Drilling Salt - Effect of Drilling Fluid on Penetration Rate and Hole
Size
“Drilling fluid selection in the past has focused on drilling a gauge
hole, with little concern on the issue of penetration
rates.(rate-of-penetration.) Drilling a gauge hole is still an
important issue for an exploration well and a critical issue for a
development well is to prevent well-bore collapse. High operating
day-cost for deep-water drilling is placing additional emphasis on
drilling rate, as reflected by the rate of penetration (ROP) and
rotating hours. This concern raises the issues of how to most
effectively improve penetration rate and/or how to drill the well bore
with a single pass. Should a water base mud (WBM) or a synthetic oil
base mud (SBM) be used. Should you drill a pilot hole and then
under-ream, under-ream while drilling, or drill without under-reaming
by using a bi-center bit? If water base muds are selected, can you use
a controlled wash-out approach to either replace under-reaming, or
make it faster? This paper will address the issue of SBM versus WBM
and the efficacy of using a controlled wash-out approach with WBM.
Case histories for the Gulf of Mexico will be discussed.”
The US Department of Energy is a good place to look for new approaches
to the problem of drill lubrication.
“Hollow glass spheres manufactured by 3M are added in volumetric
concentrations up to 50 percent to reduce the density of drilling and
completion fluids. For example, adding 50 percent microspheres to an
8.5 ppg mud, reduces its density to 5.84 ppg without the addition of
air”
From a DOE PDF file:
http://www.netl.doe.gov/publications/proceedings/99/99oil&gas/ng3b-7.pdf
The following report may help you decide which lubricant to use:
http://www.oilworks.com/New/exploreb.html
“During drilling, a continuous flow of drilling ‘mud’ is circulated
In the well. This mud is actually a thick mix of clay and other
chemical additives in water or mineral oil, as well as barite
(barium sulphate), which adds weight. Drilling mud lubricates the
bit, contains pressures, keeps the hole from collapsing and flushes
rock chips and drill cuttings to the surface.
Two basic types of drilling fluids, or muds, are used in offshore
exploration and production: water-based and oil-based muds.
Water-based mud is made up of clay (bentonite) and water; it may
include barite, a heavy mineral used to add weight. Chemical
additives are mixed in to stabilize the drilling fluid during use,
and to reduce corrosion and bacterial activity.
Oil-based mud is a mixture of barite, mineral oil, and chemical
additives. Oil-based muds are used for deeper well sections, and
in cases where the well is drilled at an angle (directional drilling),
where there is an increased likelihood for a drill pipe to stick.
Oil-based
mud is more expensive and has more negative environmental effects
compared
to water-based mud.
In recent years, a new family of synthetic-based muds
has become available in which the mineral oil component is replaced by
artificial oil-like substances. These new muds were developed in the
hope of
better environmental performance than oil-based muds. However, they
are not widely used because they are expensive, and it is still
unclear whether their performance meets expectations. “
Other links of interest to you:
http://www.csiro.au/news/ach9798/petrol98.htm
http://uk.dir.yahoo.com/business_and_economy/business_to_business/engineering/geologic_and_petroleum_engineering/geotechnical_drilling/
www.iadc.org/dcpi/dc-marapr00/f-problems.pdf
I hope this helps, if anything is unclear, please request a
clarification.
Sincerely,
Colin
Google search queries:
oil well drilling +"wet tree" deepwater +"drilling fluid"
oil well drilling techniques deep water +"drilling fluid" |
Clarification of Answer by
colin-ga
on
18 Jul 2002 08:07 PDT
Dear Mannu:
I have delved deep into your question(s) and understand your dilemma
in choosing the correct fluid for deep water drilling. These questions
have been discussed and documented for many years. Experts in the
field are still debating the time/cost/environmental variables with
all choices whether it be WBM, SBM or newer emerging mud mixes.
I will attempt to steer you to papers that discuss your problems in
great detail.
Regarding wettability and overwetability, some of your concerns are
addressed in this paper:
http://speonline.spe.org/cgi-bin/viewpaper.cgi?paper=00018476
“The wettability of typical drill solids and mud weighting agents in
simple oil-based drilling fluids was studied with a newly developed
dynamic Wilhelmy plate technique. Thin plates were cut from mineral
plate technique. Thin plates were cut from mineral specimens and used
for wettability testing without polishing. The fluid systems studied
were polishing. The fluid systems studied were equilibrated brine with
oils containing typical additives such as emulsifiers and organophilic
clays.”
With respect to reservoir descriptions, this is discussed in detail
here:
http://speonline.spe.org/cgi-bin/viewpaper.cgi?paper=00062928
“Typical reservoir descriptions may contain tens of millions of cells,
while serial finite difference reservoir simulators can generally
accommodate only a few hundred thousand cells. Thus the issue of scale
up, in which the detailed geological model is coarsened to a size
amenable to flow simulation, is one of great importance. As the
reservoir descriptions grow in complexity, several new features enter
into the reservoir description and these must be accommodated within
the scale up and flow simulation tools.”
The June 2002 issue of SPE Reservoir Evaluation & Engineering features
“On Near-Wellbore Modeling and Real-Time Reservoir Management”
discusses reservoir simulation models, and available software that
will help you determine the optimal method for deep water drilling.
The software that is used is described in this article:
http://www.spe.org/spe/cda/views/journal/speJournalMaster/0,1510,1648_2308,00.html
Second Generation Synthetic Fluids in the North Sea: Are They Better?
http://speonline.spe.org/cgi-bin/viewpaper.cgi?paper=00035061
“This paper examines and describes SBM systems recently developed as
substitutes for conventional drilling muds. Initially, background
information on drilling mud is presented to provide an overview. The
paper identifies the advantages and disadvantages of alternative
drilling muds and assesses their comparative environmental impact and
cost/benefit. The paper also characterizes the regulatory factors
which affect the introduction and widespread use of innovative
alternative mud technology.”
From the SPE report entitled
“Synthetic Drilling Muds: Environmental Gain Deserves Regulatory
Confirmation”
http://speonline.spe.org/cgi-bin/viewpaper.cgi?paper=00029737
Cementing and bonding problems:
The following paper seems to address your poor bonding problem and
attempts to improve your cementing success in deep water oil well
drilling:
“The objective in primary cementing is to displace the drilling fluid
with cement that will bond to the formation and casing to prevent
communication through the annulus. The predominant cause of failure
appears to be channels of gelled mud that remain in the annulus after
cementing. Past investigations have noted many procedures that could
improve the displacement process. These procedures include
centralization, chemical preflushes, mechanical mud cake removers,
controlled flow rates in certain regimes, pipe movement and control of
mud and cement properties.
Not until recently have the effects of many of these procedures been
isolated so that their individual importance could be determined. In a
recent paper, a comprehensive and analytical laboratory study of
various factors controlling the displacement process concluded that
there are three major factors in obtaining complete mud displacement
by the cement slurry.
1. Good relative rheological properties between the mud and cement.
The cement should be heavier and have a yield point and plastic
viscosity higher than the mud being displaced. Buoyancy forces often
can dominate the displacement process.
2. High degree of standoff or centralization. The more centered the
casing, the greater the likelihood of complete mud displacement and
removal.
3. Pipe movement obtained by rotation or reciprocation. often
unfavorable rheological properties between the mud and cement, and
poor standoff can be compensated by pipe movement. “
From:
http://speonline.spe.org/cgi-bin/viewpaper.cgi?paper=00001919
“This first critical aspect of the said effective execution is
heavily dependent on the adequate functional operation of the liner
hanger, which is lowered and set to hang-off the casing string.
Whether it is done mechanically or hydraulically (according to the
type of liner), the liner hanger must be set without affecting the
condition of the hole to be cemented or the integrity of the seals of
the tool.1”
http://speonline.spe.org/cgi-bin/viewpaper.cgi?paper=00069621
‘Remedial (squeeze) cementations to correct uncontrolled flow behind
casing are not only time-consuming and expensive, but they also weaken
the integrity of the casing. Our cementing research along with other
work has focused on methods to increase the success rate of primary
cementing. This report sets out to explain the primary cementing. This
report sets out to explain the need for a total-job-design approach to
cementation. It is shown how drilling and cementing variables together
with Correct cement formulations can lead to efficient displacement of
the drilling mud from the casing annulus. A theoretical model has been
developed to explain how a dense cement, with more than sufficient
hydrostatic head to control the formation fluids, loses its
overpressure, which can result in annular (gas) flow. This theoretical
model is used to define values of cement-formulation variables, which
will increase the chance of successfully achieving zonal isolation.‘
From:
http://speonline.spe.org/cgi-bin/viewpaper.cgi?paper=00009599
I do realize that you are looking for definitive answers to these
questions. The various methods involved are extremely complex and
differ with each application. I do not purport to be an expert in this
field, I am however an expert in finding information, papers that are
written by experts in this field. There are hundreds of methods that
experts are still debating as to the “correct” method. I can point you
in the right direction for finding the information you need, but
cannot provide an in depth comparison and debate on the merits and
shortfalls of any one method. These topics are covered in full by the
links I have provided, and are written by people that are experts in
their respective fields. I truly believe, that after reading these
articles you will be able to reach an informed decision regarding the
correct approach to your endeavor.
Sincerely,
Colin
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