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Project proposals within drilling technology, 2014, from Pål Skalle
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Topic
potential
Candidates
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Pressure loss calculator
Surge & Swab calculator
Breaking of gelled mud
Upgrading of hook load model / lab test
Identify abnormal deviation
Identify restriction – indicator
Displacement profile vs. turbulent boundary layer
Cementing of the 12 ¼ “ annulus
Cement quality control
Causes behind cementing errors
Test cement displacement
Wellbore stability
Displacement
Include case study / lab test
Hardness / pore pressure / lab test
Dias A
Andreas K
Tatiana
Kristoffer H
Christina S
Maria B
Sera F
taken?
Vegard R
Lise L
Elskan
Faustine K
Carlos T
Asgeir
Thomas
More specification of the tasks:
1.
Develop a pressure loss calculator. Make an interface which is unbeatable, either as Matlab or Excel, show
on my home page and how to copy the program by others
2.
Develop a swab pressure model. Later it must be tested experimentally (in the IPT flow / friction loop),
with and without pump running. Include flowing well. Compare with other methods. Test against field data.
Make it user friendly
3.
Breaking of gelled mud. Investigations in our rheometer and possibly in IPT flow loop. Your MSc must be
taken at your home Department. Else
Suggest how to use the knowledge in a model of breaking the gel while starting the pump. It will break up
successfully along the wellbore.
Use result from previous projects
Perform more measurements in advanced rheometer
Make model of when gel is breaking when pump is started
Non-Newtonian fluids can be characterized through their rheology. However, the settling of cuttings in
quiescent liquids and in flowing liquids can best be expressed through the low-shear-rate (low end)
rheology. The candidate will formulate the goals of the thesis on basis of this note. The preliminary tasks of
this master thesis are.
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4.
Investigate experimentally the cuttings transport process in stagnant fluids (slip velocity). Variables
should be cuttings size and shape, rheology, still-standing time, vibration, etc. The candidate
determines the test matrix and the variables, depending on the goals.
Investigate theoretically cuttings transport (slip velocity etc.) in flowing liquids, depending on the
goals
Give a recommendation of how to characterize the rheology for cuttings transport purposes (is
common rheology reporting procedure sufficient?).
Upgrade Hook Load model, evaluate observed measurements and compare with field data. Axial
friction in a well during tripping in and out. Model of cuttings accumulating. Improve theoretical model
to included well trajectory vs. side forces. Make a mathematical model of the HKL-signature which
describes the process of cuttings resistance. A classical strategy will be followed:
Understand the physics of the process
Determine all forces involved and their boundary conditions
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Develop the models
Solve and simulate numerically and test the results
Compare with field cases. Adjust models accordingly until acceptable similarity is obtained
The model is initiated, as a force – string – spring system. Viscous and side forces need to be added.
Start with existing and take it from there.
5.
At IPT we have a package of real-time drilling data (RTDD) from two wellbore sections including the two
end-of-well (EOW) reports. Drilling data are recorded every 5 th second. A major oil company has made
available a link to their own data base. This base contains data from 6 wells drilled in the 17 ½“ section (the
overburden). A reading / translation program is included in the data access. The data base contains also
some memory-stored data. The projects listed below will take advantage of the RTDD to some degree.
Most of the tasks listed below are related to restrictions, often seen during tripping operations. Study RTDD
and find some of the restrictions. Then reveal some of these secrets through a theoretical estimation of the
probability of its occurrence: Identify type of deviations from normal behavior of interesting parameters.
Changes could indicate:
Simple restrictions
Narrow wellbore
Shoveling of cuttings
ECD-cyclic load indicator
Hole cleaning indicator
6.
Identify restrictions indicators in each of the responding parameters vs. manipulated parameters:
Indicators:
ROP
HKL
Torque
Wellbore instability indicator
Sag factor
Main manipulating parameter:
BPOS
BPOB
RPM
Mechanical friction / drag indicator modelling of surface hook load signals when tripping out through incooperative cuttings bed
With increasing quality of drilling parameters, our hypothesis is that wellbore restrictions can be identified
through modelling of the surface response. Restrictions that seem relatively similar in the surface hook load
(HKL) while tripping have completely different causes:
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Accumulated material; cuttings, cavings, barite, filter cake
Larger pieces of rocks or blocks; falling-in from the wellbore ceiling from weak and unstable
formations
Hole enlargement with shoulders and ledges; dissolution and erosion of weak formations
Changes in the wellbore path; local dogleg, longer build and drop sections
Key seats; evolving in build and drop sections
If the type of restriction can be determined, and thus revealing the cause behind the restriction, the treatment of
the problem will become more purposeful and efficient. We claim that different causes will result in completely
different repair strategies. Selecting the wrong repair strategy may even worsen the situation instead of
improving it. The desire to determine the cause of physical restrictions in the wellbore is therefore the driving
motivation in this project.
Normal HKL signals are initially determined and characterized during normal process conditions, forming a
moving reference signal.
Deviatoric HKL behavior must be studied in many wells and under different process conditions. 50 cases would
make up a sufficient statistical case bank. Different wellbore restriction types will give different HKL-signatures.
The signatures will initially be approached in a simplified manner by simply grouping the cases into two types;
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cuttings restrictions and other restrictions. A hypothesis is formed of the physical explanation behind each
signature.
Collect 30 different cases which are initially assumed to resemble cuttings restrictions and 20 cases of other
restriction types. Describe the cases sufficiently detailed for later mathematical simulation; wellbore and drill
string geometry; drilling fluid characteristics; the drilling operation; the lithology etc.
The field data are obtained from Statoil. Norwegian Universities are being granted access to Statoil-data through
their Discovery Web (ref. Flemming Stene).
Figure 1 presents the activity of tripping-out one stand (30 m) through a well which is properly cleaned, and
therefore represents smooth, normal hook load behavior. We define the hook load behavior as normal when there
are no high peaks in the hook load signature.
Hook load
ck
Blo
ion
sit
po
Figure 1: Normal tripping operations of one stand through an 8 ½” hole in a vertical well. The operation
takes typically 3 minutes. The hook load tension is more or less constant and represents normal downhole
conditions.
Figure 2 represents two abnormal situations. In both cases we see high peaks initially. The peaks are triggered by
bringing a drill string, which have been quiescent for some minutes, out of rest. A corresponding negative HKLresponse is often seen immediately after jerking loose the drill string. In both plots it seems probable that
cuttings are being accumulated, and the resistance is being increased in an axial stick-slip motion. The cuttings
are alternately being shoveled; gradually more cuttings are being accumulated and jammed in narrower parts of
the wellbore and finally being compressed and finally crushed. Hard stringers (narrow wellbore) combined with
soft stringers (enlarged wellbore) can often be an indicative symptom of such behavior.
Hook load
Bloc
n
sitio
k po
Hook load
Bloc
n
sitio
k po
Figure 2: Abnormal behavior during tripping in longer horizontal sections (red line
– acceleration). The x-axis is the time scale in both plots, approximately 3 min across.
Upper figure – Cuttings restriction in relatively smooth, horizontal wellbore
Lower figure – Cuttings piling up in a more uneven, horizontal wellbore
7.
The displacement profile of the cement / drilling fluid becomes very sharp, causing the cement to mix with
the mud and thus reducing its quality. This is a problem only when the displacement process is taking place
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in laminar flow, which mostly is a necessary requirement due to ECD restrictions. One factor contributing
to improved displacement is the existence of local turbulence at the wall. The local turbulence is caused by
the roughness of the wall; either the wall is composed of the open wellbore or the casing and its equipment.
It is necessary to investigate what is determining the level of turbulence or what is causing the onset of
turbulence. This cannot be determined only theoretically because the theory is complex and depending on
many factors. A simple experiment must be designed to reveal some of the secrets behind the onset of
turbulence in laminar flow past uneven surfaces.
8.
Cement the 12 ¼ “ casing
9.
Qualify 3-5 cement recipes for sustainable sealing. All necessary tests, instruments, procedures and quality
checking issues should be included. Lab facilities at two laboratories are at your disposal.
10. On basis of several accidents, create a knowledge model which can contribute to reveal the main cause in
real time
Lab test:
a.
b.
Determine max pulling force
Determine final concentration