2. Oil blocks in Kurdistan region-Iraq [11] .

Figure 3. Drilling, survey and mud data [13] .

Beside all the above collected data there were an accurate calculations for pore pressure for different penetrated geological formations till the target which was in Qamchuqa formation as it is clear in Table 2 below.

6. Well Control Operation

Here we study and discuss the drilling operation to control the well kicks in term

Figure 4. Drilled sections in Bn-1.

Table 1. Drilled sections data [12] .

Table 2. Calculated pore pressure Bn-1.

of time in Bn-1 as a case study. During the drilling operation, there was a lot of time spend to control the BHP. The total of about 5 days with a full operation was spent to control the well. Similar scenario or worse happened in many other oil blocks in Kurdistan. There was an indication of Loss of Circulation (LOC) in the upper part of the production section after 2800 m and then kicks during the sliding drilling from 3630 m down. First pumping of Loss Circulating Materials (LCM) was at the upper part of the production section as a reaction of LOC. After that was an increase in pit volume up to 10 bbls [13] . The normal standard action was shut-in the well and monitoring the pressure started.

Seven circulation stages with different mud properties and pumping a lot of LCM to control LOC the well was not controlled totally. The main changes were in the mud density starting from 8.6 ppg and going to reach 12.1 ppg at the seventh circulation stage during the implementation of Driller Technique. Engineer and Volumetric Techniques also have been implemented to control the well. Figures 5-7 show some stages of circulation to control the well with the first kick control technique.

Figure 5 shows all the seven circulations starting from 8:25 February 12, 2010, as we can observe that the pressure are going to fluctuate with a very big difference in drill pipe pressure and casing pressure. Circulation No. 7 was the last attempt in use of Driller method but still there is no certain confidence that the well have been controlled.

As can be seen there were two problems at the same time loss of circulation and kicks. This situation has been shown in the Figure 6 in yellow color we still

Figure 5. Summary of seven circulations attempt to control the kicks with Driller method.

Figure 6. Circulations No. 3 in attempt to control the kicks with Driller method.

there is some loss.

Directly after the Driller Method, Volumetric Methods were implemented starting with increasing the mud density from 9.3 ppg to 12.1 ppg to control the well and reach the situation of SIDPP and SICP to be zero psi [12] . Changes in the drill pipe pressure and casing pressure during February 15 and 16, 2010 for about 30 hours are shown in Figure 8 and Figure 9.

Figure 7. Circulations No. 7 in attempt to control the kicks with Driller method.

Figure 8. Volumetric attempt to control the kicks.

Figure 9. Volumetric attempt to control the kicks.

The process of well controlling took 5 days and this was a high cost and increased the Non-Production Time (NPT) also. Table 3 shows the total time spent in different well control techniques to control the kicks.

7. Discussion

Driller’s Method was first implemented in the case study well. The crew proceeded immediately to displace the gas influx. The required calculations were made on the kill-weight. Circulating the kill mud was not easily displaced and the drilling operation was resumed very slowly. One of the most disadvantages of the Driller’s Method is that at least two circulations are required to control the well. In our case there were seven circulations which took a lot of time. After Driller method there were a decision to start implementing the Wait and Weight (Engineer Method) which is slightly more complicated but offers some distinct advantages. The most main advantages of the Engineer Method are the well will be killed in half the time [3] . The use modern mud-mixing facilities permit barite to be mixed at high rates, to make the time required to weight up the suction is minimized and kill rate reached quickly in the term of the time. The primary disadvantage in this method is the potential for errors and problems while displacing the kill-weight mud to the bit [9] . In Driller’s Method, the procedure can be stopped and started easily. While stopping and starting when using the Wait and Weight Method (Engineer Method) is not as easy, especially during the period that the kill-weight mud is being displaced to the bit. With taking all considerations, the Wait and Weight Method is the preferred technique compared with the driller method.

Here in Bn-1 different controlling method have been used due to uncertainty about which one is the most suitable one. Within upper part of the near the Pay Zone Interval there were LOC and within the lower part there were kick problem. Any improvements on the drilling fluid properties give different results on upper and lower part of the section.

8. Conclusions

There are many well controlling methods; each has its advantages or disadvantages in a particular location or drilling operation situation. In our case study extending the setting point of the production casing pipes to deeper setting point between 2300 m to 2500 m in Shiranish formation will isolate the problematic interval more and more. Application of the Wait and Weight Method may even

Table 3. Time spend to control the kicks.

give us higher shoe pressures if the drill pipe pressure schedule is not calculated and followed properly.

Drilling near the target zone and the liner section in Shiranish formation with new mud system of liner increase of density, viscosity and gel strength makes the drilling operation more free problematic operation. Most of the times there will be difficulty in following properly some methods like W&W. The Driller’s Method is not also a preferred method all the times. Drilling the near pay zone interval with increased mud density, viscosity and gel strength without waiting for kick indication will result in saving more time and cost. Drilling long intervals with different geological properties above the target makes the kick controlling more difficult. Any decrease in NPT means more production and optimized operation economically. Any decrease in NPT means more friendly environmental operation in the area in term of pollution.

9. Future Operations

Avoid using one fluid system in drilling loss interval and pressured interval together. Using the Driller Method with implementing the equation of hydrostatic pressure plus a safety margin of 500 psi will serve the operation of drilling in term of time above the target. This means that Pore pressure (Pp) will be:

Cite this paper
Darwesh, A. , Rasmussen, T. and Al-Ansari, N. (2017) Kicks Controlling Techniques Efficiency in Term of Time. Engineering, 9, 482-492. doi: 10.4236/eng.2017.95028.
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