Field Appraisal

If an exploratory well shows that hydrocarbons are present, more seismic data is gathered and then a number of appraisal wells are drilled and more data is collected. From th__ __ 1) data i__ 2) is poss__ __ __ __ 3) to esti__ __ __ __ 4) how mu__ __ 5) oil a__ __ 6) gas t__ __ 7) field cont__ __ __ __ 8), how diff__ __ __ __ __ 9) it wi__ __ 10) be t__ 11) extract a__ __ 12) what perce__ __ __ __ __ 13) of t__ __ 14) oil a__ __ 15) gas c__ __ 16) be extr__ __ __ __ __ 17). Unfortunately, i__ 18) ’s n__ __ 19) possible t__ 20) get ev__ __ __ 21) last dr__ __ 22) of o__ __ 23) out o__ 24) a reservoir - i__ 25) the No__ __ __ 26) Sea, f__ __ 27) example, oper__ __ __ __ __ 28) expect t__ 29) recover ab__ __ __ 30) 40 - 50% of t__ __ 31) total rese__ __ __ __ __ 32). This fig__ __ __ 33) may se__ __ 34) quite l__ __ 35), but reme__ __ __ __ 36) there i__ __ 37) ’t a la__ __ 38) of o__ __ 39) and g__ __ 40). Instead i__ 41) is tra__ __ __ __ 42) in t__ __ 43) pores o__ 44) the rese__ __ __ __ __ 45) rock a__ __ 46) you c__ __ 47) appreciate th__ __ 48) it i__ __ 49) ’t poss__ __ __ __ 50) to g__ __ 51) every la__ __ 52) drop o__ __ 53). Think ba__ __ 54) to t__ __ 55) idea th__ __ 56) oil i__ 57) held i__ 58) pores i__ 59) much t__ __ 60) same w__ __ 61) that wa__ __ __ 62) is he__ __ 63) in a spo__ __ __ 64). We kn__ __ 65) that i__ 66) isn’__ 67) possible t__ 68) get ev__ __ __ 69) last lit__ __ __ 70) drop o__ 71) water o__ __ 72) of a spo__ __ __ 73) - it’__ 74) always a b__ __ 75) damp. O__ __ 76) exploration invo__ __ __ __ 77) lots o__ 78) people wi__ __ 79) different ski__ __ __ 80), for exa__ __ __ __ 81) geologists, geophy__ __ __ __ __ __ __ 82), surveyors, mudlo__ __ __ __ __ 83), computer scien__ __ __ __ __ 84), marine biolo__ __ __ __ __ 85), drilling engi__ __ __ __ __ 86), the dril__ __ __ __ 87) crew. Alongside these are all the people employed back onshore for example economists, planners, lawyers, IT specialists, environmental advisers and safety advisors to name a few.

4. Miscible methods

One method of enhanced recovery is based on the injection of natural gas either at high enough pressure or containing enough petroleum gases in the vapour phase to make the gas and oil miscible. This met__ __ __ 1) leaves lit__ __ __ 2) or n__ 3) oil beh__ __ __ 4) the dri__ __ __ __ 5) gas, b__ __ 6) the relat__ __ __ __ __ 7) low visc__ __ __ __ __ 8) of t__ __ 9) gas c__ __ 10) lead t__ 11) the bypa__ __ __ __ __ 12) of la__ __ __ 13) areas o__ 14) oil, espec__ __ __ __ __ 15) in reser__ __ __ __ __ 16) that a__ __ 17) not homog__ __ __ __ __ __ 18). Another enha__ __ __ __ 19) method i__ 20) intended t__ 21) recover o__ __ 22) that i__ 23) left beh__ __ __ 24) by a water__ __ __ __ __ 25) by put__ __ __ __ 26) a band o__ 27) soaplike surfa__ __ __ __ __ 28) material ah__ __ __ 29) of t__ __ 30) water. T__ __ 31) surfactant cre__ __ __ __ 32) a very l__ __ 33) surface ten__ __ __ __ 34) between t__ __ 35) injected mate__ __ __ __ 36) and t__ __ 37) reservoir o__ __ 38), thus allo__ __ __ __ 39) the ro__ __ 40) to b__ 41) ”scrubbed” cl__ __ __ 42). Often t__ __ 43) water beh__ __ __ 44) the surfa__ __ __ __ __ 45) is ma__ __ 46) viscous b__ 47) addition o__ 48) a polymer i__ 49) order t__ 50) prevent t__ __ 51) water fr__ __ 52) breaking thr__ __ __ __ 53) and bypa__ __ __ __ __ 54) the surfa__ __ __ __ __ 55). Surfactant floo__ __ __ __ 56) generally wo__ __ __ 57) well i__ 58) noncarbonate ro__ __ 59), but t__ __ 60) surfactant mate__ __ __ __ 61) is expe__ __ __ __ __ 62) and la__ __ __ 63) quantities a__ __ 64) required. O__ __ 65) method th__ __ 66) does se__ __ 67) to wo__ __ 68) in carb__ __ __ __ __ 69) rock i__ 70) the inje__ __ __ __ __ 71) of car__ __ __ 72) dioxide, eit__ __ __ 73) alone o__ 74) in conju__ __ __ __ __ __ 75) with nat__ __ __ __ 76) gas. T__ __ 77) carbon dio__ __ __ __ 78) can gre__ __ __ __ 79) improve reco__ __ __ __ 80), but ve__ __ 81) large quant__ __ __ __ __ 82) at a reaso__ __ __ __ __ 83) price a__ __ 84) necessary. Most of the successful projects of this type depend on tapping and transporting (by pipeline) carbon dioxide from underground reservoirs.

5. Thermal methods

There are many reservoirs, usually shallow, that contain oil which is too viscous to produce well. Nevertheless, thr__ __ __ __ 1) the appli__ __ __ __ __ __ 2) of he__ __ 3), economical reco__ __ __ __ 4) from th__ __ __ 5) reservoirs i__ 6) possible. He__ __ __ 7) crude oi__ __ 8), which m__ __ 9) have a visc__ __ __ __ __ 10) up t__ 11) one mil__ __ __ __ 12) times th__ __ 13) of wa__ __ __ 14), will sh__ __ 15) a reduction i__ 16) viscosity b__ 17) a factor o__ 18) 10 for ea__ __ 19) temperature incr__ __ __ __ 20) of 50° C (90° F). T__ __ 21) most succe__ __ __ __ __ 22) way t__ 23) raise t__ __ 24) temperature o__ 25) a reservoir i__ 26) by t__ __ 27) injection o__ 28) steam. I__ 29) the mo__ __ 30) widespread met__ __ __ 31), called st__ __ __ 32) cycling, a quan__ __ __ __ 33) of st__ __ __ 34) is inje__ __ __ __ 35) through a we__ __ 36) into a form__ __ __ __ __ 37) and all__ __ __ __ 38) time t__ 39) condense. Conden__ __ __ __ __ __ 40) in t__ __ 41) reservoir rele__ __ __ __ 42) the he__ __ 43) of vapori__ __ __ __ __ __ 44) that w__ __ 45) required t__ 46) create t__ __ 47) steam. Th__ __ 48) the sa__ __ 49) well i__ 50) put o__ 51) production. Af__ __ __ 52) some wa__ __ __ 53) production, hea__ __ __ 54) oil fl__ __ __ 55) into t__ __ 56) well bo__ __ 57) and i__ 58) lifted t__ 59) the sur__ __ __ __ 60). Often t__ __ 61) cycle c__ __ 62) be repe__ __ __ __ 63) several ti__ __ __ 64) on t__ __ 65) same we__ __ 66). A less com__ __ __ 67) method invo__ __ __ __ 68) the inje__ __ __ __ __ 69) of st__ __ __ 70) from o__ __ 71) group o__ 72) wells wh__ __ __ 73) oil i__ 74) continuously prod__ __ __ __ 75) from ot__ __ __ 76) wells.

A__ 77) alternate met__ __ __ 78) for hea__ __ __ __ 79) a reservoir invo__ __ __ __ 80) the combu__ __ __ __ __ 81) of a pa__ __ 82) of t__ __ 83) reservoir o__ __ 84) and i__ 85) called i__ 86) situ combu__ __ __ __ __ 87). Large quant__ __ __ __ __ 88) of compr__ __ __ __ __ 89) air mu__ __ 90) be inje__ __ __ __ 91) into t__ __ 92) oil zo__ __ 93) to sup__ __ __ __ 94) the combu__ __ __ __ __ 95). The opt__ __ __ __ 96) combustion tempe__ __ __ __ __ __ 97) is 500° C (930° F). T__ __ 98) hot combu__ __ __ __ __ 99) products mo__ __ 100) through t__ __ 101) reservoir t__ 102) promote o__ __ 103) production. In situ combustion has not seen widespread use.

6. The turbodrill

One variation in rotary drilling employs a fluid-powered turbine at the bottom of the borehole to produce the rotary motion of the bit. Known a__ 1) the turbo__ __ __ __ __ 2), this instr__ __ __ __ __ 3) is ab__ __ __ 4) nine met__ __ __ 5) long a__ __ 6) is ma__ __ 7) up o__ 8) four ma__ __ __ 9) parts: t__ __ 10) upper bea__ __ __ __ 11), the tur__ __ __ __ 12), the lo__ __ __ 13) bearing, a__ __ 14) the dr__ __ __ 15) bit. T__ __ 16) upper bea__ __ __ __ 17) is atta__ __ __ __ 18) to t__ __ 19) drill pi__ __ 20), which eit__ __ __ 21) does n__ __ 22) rotate o__ 23) rotates a__ 24) a slow ra__ __ 25) (6 to 8 revol__ __ __ __ __ __ 26) per min__ __ __ 27)). The dr__ __ __ 28) bit, mean__ __ __ __ __ 29), rotates a__ 30) a much fas__ __ __ 31) rate (500 t__ 32) 1,000 revolutions p__ __ 33) minute) th__ __ 34) in conven__ __ __ __ __ __ 35) rotary dril__ __ __ __ 36). The po__ __ __ 37) source f__ __ 38) the turbo__ __ __ __ __ 39) is t__ __ 40) mud pu__ __ 41), which for__ __ __ 42) mud thr__ __ __ __ 43) the dr__ __ __ 44) pipe t__ 45) the tur__ __ __ __ 46). The m__ __ 47) is dive__ __ __ __ 48) onto t__ __ 49) rotors o__ 50) the tur__ __ __ __ 51), turning t__ __ 52) lower bea__ __ __ __ 53) and t__ __ 54) drill b__ __ 55). The m__ __ 56) then pas__ __ __ 57) through t__ __ 58) drill b__ __ 59) to sc__ __ __ 60) the ho__ __ 61) and ca__ __ __ 62) chips t__ 63) the sur__ __ __ __ 64). The turbo__ __ __ __ __ 65) is cap__ __ __ __ 66) of ve__ __ 67) fast dril__ __ __ __ 68), but t__ __ 69) bit a__ __ 70) bearings we__ __ 71) quickly i__ 72) the ha__ __ __ 73) environment. Turbodrills were widely used in the former Soviet republics of Russia and Central Asia, but they are rare elsewhere.