DRILLING FLUID LOSSES CIRCULATION INVESTIGATION MECHANISM AND SOLUTION IN BASRA OIL FIELDS

1. Basrah University of oil &gas
College of engineering for oil &gas
Names of group:
• Hassan Hadi Anad
• Naeem mashkour
• Falah hassan Othman
DRILLING FLUID LOSSES CIRCULATION INVESTIGATION MECHANISM AND SOLUTION IN BASRA OIL
FIELDS

2.  Introduction
This research focus on curing the loss circulation problems in southern
Iraq fields. Thus, afield data has been collected and investigated to obtain
the main causes of this drilling events. The great majority of the non
productive time in drilling operations is caused by the loss circulation in
southern Iraq especially in the intermediate section of Mishrif well . The
main thief zones in this section are, Hartha formation that is composed Of
dolomite in the upper part and marl in the lower part , shows in figure (1-
1) “ one of the wells in west Qurna field in southern Iraq”. One of the
sever problem in this formation is the loss of drilling fluids in whole or in
part due the presence of natural fractures. The other problematic formation
in this section is Dammam formation that consists of permeable dolomite.

3. Figure (1-1) shows one of the wells in west Qurna field in southern Iraq
Figure 1-1 - shows one of the wells in west Qurna field in southern Iraq

4.  Lost circulation
Lost circulation is oldest common problems in drilling well that cause’s
increase in drilling wells cost so it’s occur in formation that high porous
,caves and induced.
 Classes of lost circulation
 Seepage losses
 Partial mud losses
 Severe mud losses
 Total mud losses

5.  Types of Lost Circulation:
Lost circulation can be broadly classified into two major categories based on the
cause of the loss:
1.Natural losses occur in formations with natural permeability, usually voids or
fractures.
2.Induced losses occur in an induced fracture, caused when hydraulic forces in the
wellbore exceed the formation strength.
However There are four main scenarios that are listed in Table (1-1) and illustrated
in Figure 2

8.  Effects
There are two basic consequences of lost circulation:
1- If the level of fluid in the well bore is lost due to losing mud inside the
formation, lower hydrostatic pressure is created which results in the flow of
fluids inside the formation into the well bore. This process is commonly
called kick.
2-if the drilling is continued to a point where there is no fluid left inside the
well bore; it can result in damage to the well bore, including the destruction
of the bit. This phenomenon is called dry drilling.

9.  Types of drilling fluid
Currently in the industry, there are four common types of drilling
fluids available, which are (Economides et al., 1998):
1) Water-based mud
2) Oil-based mud (OBM)
3) Synthetic-based mud
4) Pneumatic drilling fluids
These fluids are affected by temperature and pressure variations,
which in turn has an effect on the physical and visco-elastic
properties and the rheology.

10.  Additives of drilling fluid
After lost circulation takes place, an effort is made to reduce the severity
of the loss by increasing the viscosity of the drilling mud by adding
certain additives, The most commonly used additives are :
1) Bentonite is used to increase the viscosity of the drilling mud which
slows the flow of fluid in the nearby formations.
2) Polymers are used for increasing the viscosity of the drilling mud, but
they are more expensive, physically.
3) Sawdust, flaked cellophane and ground gypsum are used to plug or seal
the sources of losses.
4) Cheaper options include shredded newspaper and cotton seed hulls,
which also act as plugs or seals.

11.  Lost Circulation Prevention
In order to prevent or reduce the effect of lost circulation, there are three
areas in the drilling operation that should be focused on:
1. Mud system design.
2. Equivalent circulating density (ECD) monitoring.
3. Selective casing design.

12. 1. Preventive Tests
lost-circulation zones are anticipated, preventive measures should
be taken by treating the mud with loss of circulation materials
(LCMs) and preventive tests such as the leak off test and
formation integrity test should be performed to limit the
possibility of loss of circulation.The prevention tests is normally
used to predict the fracture gradient of the formation. Thus the
optimum mud density to mitigate the loss circulation is proposed.

13.  Leak off test (LOT)
Test to determine the strength or fracture pressure of the open formation
usually conducted immediately after drilling below a new casing shoe.
During the test, the well is shut in and fluid is pumped into the wellbore to
gradually increase the pressure that the formation experiences. At some
pressure, fluid will enter the formation, or leak off, either moving.

14. Stress cage is considered as a method of strengthening the wellbore by increasing
the fracture resistance of the formation. The concept behind stress cages is that
small fractures are induced, and thereafter introduced to particles in the mud that
allows the fracture to stay open.
2. Stress Cage

15. Various wellbore strengthening concepts have been developed for stabilizing wellbores to control mud
losses, especially in sections with narrow mud weight windows between the wellbore collapse and fracture
gradients. These include physical methods, such as plastering or otherwise minimizing fluid interaction with
the wellbore; chemical methods Such as osmotic mechanisms for controlling pore fluid dynamics; thermal
methods, such as heating the wellbore to tighten the rock and impart to it additional tangential stress.
3.Wellbore Strengthening Theory:

16.  Remedial measures
In cases where lost circulation has already occurred, there are measures for preventing the situation from
developing further, by either controlling the lost circulation or by attempting to seal off the interval where there
is loss of circulation ,These measures includes:
1. Removal of the conditions that causes the lost circulation, thereby allowing
2. the formation to heal itself
3. Bridging off the lost circulation interval by adding lost circulation material(LCM) or drilled solids
4. Spotting a high-viscous plug across the interval
5. Squeeze cementing in the interval
6. Setting pipe across the interval
7. Either abandon or sidetrack the interval.
The type of measure, or in some cases the combination of the measures will be selected based on the
location, type and severity of the problem.

17.  Detection of Natural Fracture by Well Log Analysis
Logs became more important in the evaluation of fractured reservoir since (1951) when Mardock and Myres and Lytle and Ricke
published techniques for evaluating the fractured spraberry trend of Texas using radioactive and induction logs. This beginning provided
reasonable results for distinguishing lithologies. However, quantitative analysis was not possible. Since then, many interpretation
techniques have been developed.
• Sonic Amplitude Logs
The sonic log was widely used to detect fractures. In 1963 , Pickett indicated that recording acoustic velocity generated by a logging tool identifies
four waves type ; ( 1) a compressional wave , (2) a shear wave , ( 3) a fluid or water wave and ( 4) a low velocity wave.
The use of induction logs to detect fracture is poor as the current flows around the borehole (in the formation) and does not flow parallel to the fracture for
more than a very short distance . But in some instance logs indicate the presence of fractures. This is possible when there are resistivity anomalies in an interval
and sufficient resistivity contrast with adjacent beds.
• Induction Logs
The SP curve often seems to exhibit some activity in front of fractured zone in the form of either erratic behavior or some systematic
deflection probably due to a streaming potential. Since the SP is not often very reliable in hard formations, this can only be used as a check
of the other indictors. Although the presence of increased shaleness around fractures has been suggested, increased gamma ray reading,
which is sometimes observed, could be more logically explained by deposition of uranium salts in the fracture.
• Caliper

18.  Locate the Exact Point of Lost Circulation
Contrary to the common believe, the majority of the losses do not occur
at the bottom of the hole. It has been established that more than half of
the losses occur just below the last casing shoe. Several methods are
available for locating the point of lost circulation. These include:
 Spinner Survey
The spinner survey is made by running a small spinner attachment into the well on a single
conductor cable in such a manner that the vaned rotor will spin or turn if there is any
horizontal motion of the mud. The rpms of the rotor are recorded on film as a series of dashes
or spaces. The rpm will be very slow until the point of loss is reached. There is a definite
increase in the rotors speed at the point of loss.

19. A common tool used to define lost circulation intervals is the temperature log. This log may be used
to record absolute temperature or differential temperature. As the logging tool is lowered down the
drill pipe, it reads an abnormal change at the loss zone if the underground flow is continuous (Fig.
1-5). The tool senses the heat from the fluid that is greater than it should be for the depth at which it
is encountered. In some cases, the temperature change is reported as a cooling effect, supposedly
due to gas expansion. Nonetheless, a temperature change is the key.
Figure 1-5 - Illustration of the expected results from a temperature log used to
locate the loss zone during an underground blowout.
• Temperature Log

20.  Radioactive Tracers
A radioactive tracer survey is used to follow the movement of fluids by introducing a radioactive isotope into the fluid. This isotope
is tracked with a gamma ray counter. The most common radioactive tracer material used in the Gulf Coast area is iodine 131. This
material has a half-life of 8.1 days and is soluble in water. Iodine 131 is placed in the borehole with a special injector tool. Each
injection puts a measured amount of solution in the borehole. This slug of tracer material is followed by movement of a gamma ray
detector. The slug can be followed from the tool to a zone of lost circulation or underground blowout. When the radioactive material
enters a zone of lost circulation it will concentrate and show an increase in radiation for that zone (Fig. 3-2). Repeat runs with the
gamma ray tool will define the location and thickness of the invaded zone.
Figure 1-6 - Radioactive log

21.  Curing Losses Circulation
• Seepage Losses
Seepage losses are frequently cured by simply reducing or stopping the pump rate and allowing the formation to heal and become
sealed off by the development of a filter cake. The pump rate can be gradually increased after the losses have stopped. If losses do not heal
by themselves and economics or other reasons dictate the amount of loss can’t be tolerated, for curing the loss must be pumped an LCM3.
• Partial Losses
Partial losses usually require treatment. However, as a first action to treat this kind of loss the bit should be pulled off-
bottom, the pump turned off and the formation should give the chance to heal by itself. If losses stop, drilling can resume
with reduced drilling fluid weight and/or pump rate, if both or either are possible. If the loss does not heal by itself the
following LCM pill.
• Total losses –of-Return
Total lost circulation, however, occurs when all the mud flows into a formation with no return to surface. Unless the
fracture is induced, losses normally cannot be stopped by pumping conventional LCM pills. The alternative is a reinforcing
plug or cement. However, a pill of LCM often is the first choice since, if successful, it delivers a quick response and it is easy to
apply. If this pill does not heal the fracture, a reinforcing plug or cement should be set across the loss zone.

22.  Precautions
1- Great care must be taken to avoid plugging the drill string when using the concentration of LCM.
2- Keep the pits well agitated. A displacement rate of around 400 gpm should be used. Never stop pumping until the
LCM is displaced to the well.
3- The LCM particles should be less than a third of the nozzle size.
4- In some circumstances, increasing the viscosity of the pills may be more beneficial than increasing the LCM
concentration.
5- Large bags of LCM should be available to aid in the rapid mixing of pills.
6- Ensure that all the restrictions in the BHA and at surface have been reduced to a minimum.

23. How to Predict the Loss of Drilling Fluids
Lost circulation can be avoided by well profile design and by calculating Pore pressure and Fracture pressure.
Figure 7-1 - Well window
profile ( mud design)

24.  Prediction of Fracture Pressure by using methods common:
1. Sh- Hubbert and Willis 1957
2. Ben Eaton
3. Breckels and van Eekelen (1981) Brunei
We choose the appropriate method for
these methods to be applied to calculate
fracture pressure gradient, through which the
drilling fluid is designed.

25. Formation
Expected
Depth
(m)
Expected
Depth (ft)
Expected
problems
Pore
Pressure
Gradient
(PSI/ft)
pore
ptessure
psi
Fracture
Pressure
Gradient
(psi/ft)
Fracture
Pressure
Gradient
(psi/ft)2
0 0 0.4 0 0.65 0
1 3.28 0.43 0.43 0.65 0.65
Upper Fars 70 229.6 0.43 30.1 0.65 45.5
Dibdiba 290 951.2 caving 0.43 124.7 0.72 208.8
Lower Fars 450 1476 Heavy oil 0.43 193.5 0.72 324
Ghar 855 2804.4 0.43 367.65 0.77 658.35
Dammam 940 3083.2 P&c losses 0.43 404.2 0.79 742.6
Rus 1210 3968.8 0.48 580.8 0.8 968
Um Er-
Raduma 1230 4034.4
Sulpher
water 0.48 590.4 0.8 984
Tayarat 1629.325 5344.186 0.48 782.076 0.82 1336.0465
Shiranish 1746.91 5729.8648 Tight hole 0.49 855.9859 0.83 1449.9353
Hartha 1881.915 6172.6812
Loss and
tight hole 0.5 940.9575 0.83 1561.98945
Shiranish 1949.814 6395.38992 Tight hole 0.5 974.907 0.83 1618.34562
Saadi 2038.848 6687.42144 0.5 1019.424 0.86 1753.40928
Tanuma 2175.521 7135.70888 caving 0.53 1153.02613 0.84 1827.43764
Khasib 2226.634 7303.35952 Tight hole 0.52 1157.84968 0.84 1870.37256
MISHRIF 2299.1515 7541.21692 0.51 1172.567265 0.84 1931.28726
TD 2526.373 8286.50344 0.51 1288.45023 0.84 2122.15332
 Design Mud Density
In well X# in WQ felid, when the drilling, Design Mud Weight Program (Range )
& Recommended value , note that surface casing will run at 1200 m.

26.  Curing lost circulation by reducing mud weight:
If a complete loss of circulation or high loss circulation rat was observed, stop the drilling, fill well with water until the annular
level remained stationary, and then prepare new mud weight. To calculate the new mud weight:
Step 1
Determine annulus capacity
Annular capacity, bbl/ft =
(𝐷ℎ)2
1029.4
Step 2
Determine height of water that added to annulus until the annular level remained stationary.
Height of water column, ft =
volum of added water,bbl
Annular capacity,bbl/ft
Step 3
Determine Formation pressure
Formation pressure = pressure due to mud column + pressure due to water column
Step 4
Determine required new mud weight
Required mud weight,ppg =
𝑭𝒐𝒓𝒎𝒂𝒕𝒊𝒐𝒏 𝒑𝒓𝒆𝒔𝒔𝒖𝒓𝒆 (𝒑𝒔𝒊)
0.05∗TVD (ft)

27.  CONCLUSIONAND RECOMMENDATION
1- Most problem occur in Basra oil field are stuck pipe, lost circulation and kick .
2-From a study a number of wells in west Qurna we conclude that losses occur in Damam, Umn-errathuma, Sadi, Hartha, Khasib, Mishrif and
Rumauli and especially in Damam and Hartha formation.
3-Often, losses occur in the last mumber of Damam formation because of its composition from vuggy and porous.
4-The volume of LCM that pumped to the hole depend on the severity of the formation so in the Hartha formation we need to pump high
amount of LCM because of its high severity compared with other formations.
5-by this study we found that LCM able to stop loss through Damam formation but it most time useless with Hartha formation so we have to
use cement plug to stop loss in drilling mud .
6-We conclude that losses cannot be avoided permanently Because it is related to the nature of the formation so plastic materials of certain
shapes have the ability to swell in the formation must be used during the drilling to seal the hole where losses going to stop or reduce .
7. The increase of the concentration of lost circulation material has a significant effect on fracture bridging and lost circulation control.
8. Use Underbalanced Drilling (UBD) technique to avoid lost circulation.

28. thanks for listening