PVT analysis of. bottom hole sample from Well by Otto Rogne. STAT01 L EXPLORATION 81 PRODUCTlON LABORATORY

Transcription

1 PVT analysis of bottom hole sample from Well STAT01 L EXPLORATION 81 PRODUCTlON LABORATORY by Otto Rogne

2 stcrtoil Den norske stats oljeselskap as Classification I Requested by J,Hanstveit, LET Bergen Subtitle Co-workers Bodil Fjareide, LAB PVT analysis of bottom hole sample from Well EXPLORATION & PRODUCTION LABORATORY by Otto Rogne Prepared Approved /7 j,/ /-

3 CONTENTS Page INTRODUCTION 2 SAMPLING CONDITIONS 3 Bubble point check Fig. 1 Bubble point at ambient FLASH OF RESERVOIR FLUID TO STOCK TANK Molecular composition Extended molecular composition CONSTANT MASS EXPANSION Fig. 2 Relative volume DIFFERENTIAL DEPLETION Molecular composition of liberated gases Molecular composition of residual oil Fig. 3 Compressibility factor, Z Fig. 4 Fig. 5 Fig. 6 Fig. 7 Reservoir oil density Gas formation volume factor Solution gas, RS Formation volume factor VISCOSITY OF RESERVOIR FLUID Fig. 8 Viscosity

4 INTRODUCTION The present report gives the experimental results of a PVTanalysis carried out on a bottom hole sample from test no. 2 on well , obtained by Stavanger Oilfield Services AIS on June 8, Sampling details are given on page 3. The quality of the sample was checked by measuring the bubble point at ambient laboratory conditions and found to be 388 barg (page 4 ), as compared to a reported field value of 380 barg at approx. ~ O C this was considered sat isfactory. A portion of the sample was charged to a high pressure cell at 0 reservoi r temperature (106 C) where the bubble point, re1 at ive volumes and compressibility were determined. These results are on page 7. To determine the reservoir fluid composition a portion of the fluid in the cell was flashed through a laboratory separator at 15O~ and atmospheric pressure. The 1 i berated gas and oi 1 were collected, measured and analysed separately by gas chromatography through C with decanes plus fraction. These results are on page 9 5. An extended reservoir fluid composition based on the above mentioned flash up to C and from C10 to C20+ on a TBP 9' distillation of stock tank oil, is given on page 6. The TBP dist i 1 lat ion is reported separately. The remaining sample in the cell was finally differentially liberated through a series of pressure steps with the results shown on page 8. The composition of the liberated gases are on page 9, and the composition of the gas free liquid remaining in the cell at atmospheric pressure on page 10. The gas viscosity were calculated from the gas density according to Lee et.at.

5 J.Pet.Techn., 997 (1966). A separate portion of the sample was charged to a high pressure rolling ball viscosimeter for viscosity measurements at ~ ~ The. results are on page 11. SAMPLING CONDITIONS We1 1 Format ion Date Test Interval 34/10-17 Brent m RKB Sample no. Sample bottle no. sample type Sample depth Bottom hole '$3gl.6 m RKB Bottom hole pressure Bottom hole temperature 409 bar 106 OC Well flowed for approx. 45 min., then closed in for approx. 10 min. before sample being taken.

6 Well: BHS BUBBLE POINT AT ROOM TEMPERATURE (Bottle nr ) Pressure Barg Pump reading cm Bubble point lab ( lgoc) = 388 barg Bubble point field ( 8'~) = 380 barg

7

8 We1 1 : 34/10-17 BHS FLASH OF RESERVOIR FLUID TO STOCK TANK CONDITIONS (Molecular Composition) Component Stock tank Evol ved ~eservoirf lui% oi 1 gas mol % mol % mol % weight % N i t rogen Carbond i ox i de ' Methane' Ethane Propane i- Butane n- Butane i- Pentane n- Pentane Hexanes Heptanes Octanes Nonanes Decanes plus Molecular weight GOR Sm /m Formation vol. factor m /m Density at bubble point : g/cm3 Density of ST0 at 15O~ : g/cm3 Gas gravity (air =1) Molecular weight of ClO+ : 316 Density of ClO+ at 15 C : g / cm3

9 We1 1 : 34/10-17 BHS EXTENDED RESERVOIR FLUID COMPOSITION Component mol % mol weight Density

10 CONSTANT MASS EXPANSION AT ~ ~. Pressure Re1 vol Compressibility Y-factor Barg V/Vb 1/Bar E E E E E E-04 Pb = E For P < Pb Y = E-03 x P For P > Pb V/Vb = E-04 x P E-07xPxP

11

12 DIFFERENTIAL DEPLETION AT 1 06' C Pressure Oi 1 form Solution Gas form Res oi 1 Compr Gas vol fact gar vol fact dens i t y factor viscosity barg Bod Rs Bg g/cm3 Z cp :: at 15 C Bod : Volume of oil at P and T per volume of residual oil Rs Bg at 15 C and atm P. : Standard m3 gas per m3 residual oil at 15 C : m3 gas at T and P per standard m3 gas

13 DIFFERENTIAL DEPLETION AT 106O C (Molecular composition of differentially liberated gas, mol%) NITROGEN 1.24 CARBONDIOXIDE 0.84 METHANE ETHANE 9.44 PROPANE 5.36 i -BUTANE 1.06 n-butane 1.83 i -PENTANE 1.02 n-pentane 0.99 HEXANES 1.09 HEPTANES 1.39 OCTANES 1.99 NONANES 0.75 MOLE WEIGHT GRAVITY (air = 1)

14 DIFFERENTIAL DEPLETION AT ~ ~ (Molecular composition of residual oil) COMPONENT MOL% NITROGEN CARBONDIOXIDE METHANE ETHANE PROPANE i -BUTANE n-butane i -PENTANE n-pentane HEXANES HEPTANES OCTANES NONANES DECANES DENSITY AT 15 C MOLE WEIGHT

15

16

17 DIFFERENTIAL DEPLETION Gas formation volume factor

18 DIFFERENTIAL 'DEPLET'ION AT 106 DEG.C SOLUTION GOR

19

20 VISCOSITY OF RESERVOIR FLUID AT 106'~ Pressure (barg) Vlscosi ty (centipoise)

21