Wellbore Instability and Borehole Breakout


Despite the fruit of glaze and steam perseverance technology, Courteous-behaved-mannered-manneredbore inconstancy sediment single of perception – efficient opportunity that require perseverance billions full year. courteous-behaved-mannered-manneredbore inconstancy has been single of the courteous-behaved-mannered-mannered-mannered planning grade and been elaborate distantly (Bradley,1979; Bell, 2003; Zhang et al., 2003; Gentzis et al., 2009; Zhang et al., 2009; Ding, 2011). Organization through a construction led to urgency changing a complete the borerecess imputable to roll dissolution. In this decomposition, mud gravity urgency is the calm parameter during the organization. The mud gravity urgency ownty can beginning span demand mechanisms which are sown demand (breakout) and tensile demand (fracturing), these problems meditate as the deep courteous-behaved-mannered-manneredbore demand. Borerecess breakout happens when the mud gravity is inferior than expected. in other order, the breakout demand occurs when the urgency imposed by organization mud inferior than compressive power. On the other agency, upper mud gravity can carry to tensile demand imputable to assault of mud into the construction. The consequences astern these problems are amass pipe, reaming performance, obsolete prevalence, and sidetracking. To eject these problems frequent parameters should be meditateed such us roll power, pore urgency, in-situ urgency, and urgency orientation. Furthermore, breakout and fracturing can be diminishing or eject by choosing the eligible mud gravity control organization. By using a constitutive specimen to forebode the urgencyes acomplete the courteous-behaved-mannered-manneredbore individualed with a demand criteria, Power of reservoir rolls can be adapted. Hence, choice of the eligible demand criteria earn meditate as the deep multiply of courteous-behaved-mannered-manneredbore possession decomposition.

Borerecess breakout is an expansion and extension of courteous-behaved-mannered-manneredbore in a multiplyicular address and it meditates as the dignified indicators to forebode the orientation of min. mawkish urgency. This expansion can be forebodeed by using 4-6 utensil caliper utensil, Optical imaging log, resistive statue log, and sharp statue log (Jaeger et al.,2009; Bell and Gough, 1979; Zoback et al.,1985).  Figure (1) pretexts courteous-behaved-mannered-manneredbore expansion specimen via 4 utensil caliper. The 4 utensils caliper has 4 pads in span calipers (pad 1 and 3) reproduce-exhifragment Caliper 1 (C1) and (pad 2 and 4) reproduce-exhifragment caliper 2 (C2). The bisection of the recess can be signed from those span calipers. Fig 1a reproduce-exhibits an in-gauge recess beginning C1 and C2 own similar balbutiation of fragment dimension. In opposition 1C pretexts a rigid washout in recess dimension and caliper balbutiation pretext this expansion.

Stand on courteous-behaved-mannered-mannered-mannered logs facts and tentative equations, the roll power and spontaneous ownties can be obtained (Rahimi, 2014). (Westergarrd. 1940) in-situ urgency can be obtained by modifiable idiosyncrasy equations. Also, from elastoplastic idiosyncrasy equation in-situ urgency can be adapted (chang et al., 2006). As courteous-behaved-mannered-mannered-mannered , (LOT) and mini frac. cupel can acceleration us to state in-situ urgencyes (Bardley 1979b).

Frequent specimens own been built to state the adventitious urgency in a round courteous-behaved-mannered-mannered-mannered and forebode the eligible mud urgency by using Demand criteria. In this decomposition, three demand criteria own been used to forebode the own mud gravity in the Nahr Umr construction in southern Iraq. The three demand criteria are Mohr-coulomb, Mogi-coulomb, and qualified lade.

Fig (1) Caliper log responses imputable to courteous-behaved-mannered-manneredbore expansion (Tingay )

Geological ownties of the scene and the target reservoir.

The H glaze filed is a land-based scene located in southeastern Iraq between the city of Basra and the Kuwait boundary (Figure 2).

The scene is an anticline that runs roughly north-west to south-southeast approximately 60 km covet and 10-15 km distant. The anticline of H scene has indelicate domes separated by saddles, from the northwest to southeast these are:

  1. Al-Hamar
  2. Shuaiba
  3. Rafidyah
  4. Safwan

Fig (3) The indelicate domes in H filed

The discovered reserves are contained in five reservoirs: Mishrif, Nahr Umr, Zubair 3rd Pay, Zubair 4th Pay and Yamama. (Figure 3) reproduce-exhibits courteous-behaved-mannered-mannered-mannered stratigraphic.

Nahr Umr Construction is an interesting immanent instil beginning zsingle imputable to the abundance of log facts through the individual, instil salinity that is consonant with the Mishrif and Zubair Construction instils, and the reputed quantity and power of the aquifer. It is secure deeply of Sandstsingle interbedded with streaks of (Shale, Siltstsingle & Limestone). Mediocre density of Nahr Umr construction is +/- 260 m and the porosity surpass 25% with an mediocre of 20% permeability ranges from 1000 md to 9000 md. Depends on inconstruction from more than fifteen courteous-behaved-mannered-mannereds, sown demand has been noticed in Nahr Umr construction distinctly at the shale layers. This breakout has been pretextn on shale shaker and by caliper log.

Fig (4) stratigraphic of H scene


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