Question

C). The following data are available for a newly discovered gas reservoir:

GWC = 9700 ft, Centroid depth = 9537 ft, Net bulk volume (V) = 1.776 × 1010 ft3, ∅ = 0.19

Swc = 0.20, γg = 0.85

Although a gas sample was collected during a brief production test, the reservoir pressure was not recorded because of tool failure. It is known, however, that the water pressure regime in the locality is Pw = 0.441D + 31 psia and the temperature gradient is 1.258°F/100 ft, with ambient surface temperature 80° F.

It is intended to enter a gas sales contract in which the following points have been stipulated by the purchaser:

§* During the first two years, a production rate build-up from zero −100 MMscf/d) must be achieved while developing the field.

§* The plateau rate must be continued for 15 years at a sales point delivery pressure which corresponds

to a minimum reservoir pressure of 1200 psia. Can this latter requirement be fulfilled? (Assume

that the aquifer is small so that the depletion material balance equation can be used).

Once the market requirement can no longer be satisfied the field rate will decline exponentially by 20% per annum until it is reduced to 20 MMscf/d. This gas will either be used as fuel in the company's operations or compressed to supply part of any current market requirement.

I. Determine the total cumulative recovery at abandonment, ultimate recovery factor and the length of the entire project life.

II. Assume that you are a Trainee Engineer with the company and was tasked to undertake the above assessment. Prepare a PowerPoint presentation based on your analysis to be presented to your senior engineers and management.

Answer 1

Sol. For answering the question first we have to find GIIP. For Calculating GBJP it is necessary to calculate bitial gus pressure at the controid depth of de reservoir. Pg awc. 0.441 X 9700 +31 = 430 9 psia And tomperature as 9700 7. =(1.258 Xgpoo ) +80 +460 = 662°R 100 Zawc=0.888 - 35.37 X 4309 0-888 X662 - 259.3 Egwe = 75-37 ZT The Pressure Gradient of gas at GwC dP Pg C E 0.076380185x259-3 = 0.117 pilet d) 144 144 '. Pressure of Cras at centroid XAD p = Pg Guc P = 4309 - 0.117 x (9700 - 9537) = 4290 psia. Absolute temperature at Centooi'el is 9537. 699.70x10°scf GII P = a = Vẻ - Soc), 1.776 X10'0 x0.19 X0.8X35.37 x 4290 G= 0.887 X660 - The overall production schedule can be divided into three parts, the build up, plateau production and decline pembels Rate ap. Gp2 Q=100 Gpa م 150 20 Ett tz

Gope = a (i - 1200/0,832 Pilza P/Z =699.70X109 * ( 4250/0.887 Apr 491:04 X109 scf doo pesid is build » The cummulative production rate during years up Gp, X2 X365 = 50X106X2X385 = 36.5X109 set hang » The gas pooduction at plateau rate of 100 MM scf ld is Gope- Capo = (491:04-3660)x103 = 454.54 xjo ºset 12.45 yrs Time for which rate is maintained GP2 - Gpi ty 454:54X109 100X10X375 0 The time for which the plateau sate sustained fall short of requirement by 2.5 yrs. Exponential dedine period Rate B = -bt t Time required for rate to fall to 20 MM schld toe en hoe om en 100 = 8:05 yrs. [adt = fto.estat (1-est) ༼ goa {9, =) Cumsunulantie gas production) 9p Whent = 8.05 yrs ! 146.02x10?scf 100 X106x365 (1-6 -6•2X8-05) gpges 0.2 =) Recovary factor 637.06X/04 o.gl or 91% GIIP Grz RF = 669.70X105 For total time of : 2+12:45+ 8.65 = 22.5 yos,

I cannot solve the last past because 'my whole time is consumed in Sowing this. You know Power Point Presentation takes time.