Wellbore Instability and Borehole Breakout

Wellbore Instability and Borehole Breakout Presentation: Regardless of the advancement of oil and gas industry innovation, Wellbore precariousness stays one of non gainful time that cost industry billions consistently. wellbore flimsiness has been one of the well arranging stage and been concentrated broadly (Bradley,1979; Bell, 2003; Zhang et al., 2003; Gentzis et al., 2009; Zhang et al., 2009; Ding, 2011). Penetrating through a development prompted pressure changing a round the borehole because of rock expulsion. In this examination, mud weight pressure is the controllable boundary during the boring. The mud weight pressure impacts can cause two disappointment instruments which are shear disappointment (breakout) and elastic disappointment (cracking), these issues consider as the principle wellbore disappointment. Borehole breakout happens when the mud weight is lower than anticipated. in other word, the breakout disappointment happens when the pressure forced by penetrating mud lower than compressive quality. Then again, higher mud weig ht can prompt elastic disappointment due to attack of mud into the development. The results behind these issues are stuck funnel, reaming activity, lost course, and derailing. To dispense with these issues numerous boundaries ought to be viewed as such us rock quality, pore pressure, in-situ stress, and stress direction. Besides, breakout and cracking can be lessening or wipe out by picking the reasonable mud weight for penetrating. By utilizing a constitutive model to anticipate the worries around the wellbore associated with a disappointment standards, Strength of store rocks can be determined. Henceforth, determination of the appropriate disappointment models will consider as the principle part of wellbore soundness examination. Borehole breakout is a broadening and stretching of wellbore a specific way and it considers as the significant pointers to foresee the direction of min. flat pressure. This amplification can be anticipated by utilizing 4-6 arm caliper instrument, Optical imaging log, resistive picture log, and acoustic picture log (Jaeger et al.,2009; Bell and Gough, 1979; Zoback et al.,1985).ã‚â Figure (1) shows wellbore extension design through 4 arm caliper. The 4 arms caliper has 4 cushions in two calipers (cushion 1 and 3) speak to Caliper 1 (C1) and (cushion 2 and 4) speak to caliper 2 (C2). The measurement of the opening can be distinguished from those two calipers. Fig 1a speaks to an in-check opening reason C1 and C2 have same perusing of bit size. Conversely 1C shows an extreme waste of time in opening size and caliper perusing show this development. Remain on well logs information and exact conditions, the stone quality and mechanical properties can be acquired (Rahimi, 2014). (Westergarrd. 1940) in-situ stress can be gotten by versatile trademark conditions. Likewise, from elastoplastic trademark condition in-situ pressure can be determined (chang et al., 2006). Also , (LOT) and smaller than usual frac. test can assist us with determining in-situ focuses on (Bardley 1979b). Numerous models have been worked to decide the incited worry in a roundabout well and anticipate the reasonable mud pressure by utilizing Failure rules. In this investigation, three disappointment models have been utilized to foresee the best possible mud weight in the Nahr Umr arrangement in southern Iraq. The three disappointment models are Mohr-coulomb, Mogi-coulomb, and changed replenish. Fig (1) Caliper log reactions due to wellbore expansion (Tingay ) Geographical properties of the field and the objective supply. The H oil recorded is a land-based field situated in southeastern Iraq between the city of Basra and the Kuwait fringe (Figure 2). The field is an anticline that runs generally north-west to south-southeast around 60 km long and 10-15 km wide. The anticline of H field has four vaults separated by saddles, from the northwest to southeast these are: Al-Hamar Shuaiba Rafidyah Safwan Fig (3) The four arches in H documented The found stores are contained in five supplies: Mishrif, Nahr Umr, Zubair third Pay, Zubair fourth Pay and Yamama. (Figure 3) speaks to well stratigraphic. Nahr Umr Formation is an intriguing potential water source zone because of the plenitude of log information through the unit, water saltiness that is perfect with the Mishrif and Zubair Formation waters, and the revealed degree and quality of the spring. It is made principally out of Sandstone interbedded with dashes of (Shale, Siltstone Limestone). Normal thickness of Nahr Umr development is +/ - 260 m and the porosity surpass 25% with a normal of 20% porousness ranges from 1000 md to 9000 md. Relies upon data from in excess of fifteen wells, shear disappointment has been seen in Nahr Umr development extraordinarily at the shale layers. This breakout has been appeared on shale shaker and by caliper log. Fig (4) stratigraphic of H field