Special petroleum pombi inonyanya kushandiswa kuchera mafuta uye gasi tsime uye kutapurirana mafuta uye gasi. Inosanganisira pombi yekuchera mafuta, casing yeoiri uye pombi yekupomba mafuta. Oiri yekubooresa pombi inoshandiswa kubatanidza chibooreso chehuro kune chibooreso uye kutamisa simba rekuchera. Oiri casing inonyanya kushandiswa kutsigira madziro etsime panguva yekuchera uye mushure mekupedzwa, kuitira kuti ive nechokwadi chekuchera uye kushanda kwakajairika kwetsime rose mushure mekupedzwa. Pombi yekupomba inonyanya kutamisa mafuta negasi kubva pasi petsime kuenda pamusoro.

Kabati yemafutandiyo nzira yehupenyu yekushanda kwetsime remafuta. Nekuda kweakasiyana mamiriro e geological, pasi pevhu kushushikana mamiriro akaomarara, kusimba, kumanikidza, kukotama uye torsional kusagadzikana kuita pane pombi muviri, iyo inoisa kumberi kwepamusoro zvinodiwa pamhando yecasing pachayo. Kana iyo casing pachayo ikakuvadzwa nekuda kwechimwe chikonzero, tsime rose rinogona kudzikiswa kugadzirwa kana kutosiiwa.

Maererano nesimba resimbi pachayo, casing inogona kugoverwa muzvikamu zvakasiyana zvesimbi, kurevaJ55, K55, N80, L80, C90, T95, P110, Q125, V150, etc. Mamiriro ezvinhu akasiyana-siyana, tsime rakadzika, kushandiswa kwesimbi giredhi zvakare kwakasiyana. Iyo casing pachayo inodiwawo kuve nekushomeka kwecorrosion munzvimbo inoora. Munzvimbo yakaoma geological mamiriro, casing inodiwa zvakare kuve nekugona kuramba kudonha.