SPE New Pore-scale Considerations for Shale Gas in Place Calculations

Transcription

1 SPE New Pore-scale Considerations for Shale Gas in Place Calculations Ray Amrose - Devon Enery, Roert Hartman - Weatherford Laoratories, Mery Diaz-Camos, I. Yucel Akkutlu and Carl H. Sondereld - University of Oklahoma

2 Overview Introduction Comarison of etrohysical models Physical evidence Concetual model Sored henomenon SEM imaes of orosity in as-shale Movie of 3D model Equation showin correction to free ore-sace Sored hase density characterization Examles of effects Conclusion

3 Introduction With the current industry-wide calculation method for total as volumes in oranic shale reservoirs, the amount of as storae has een overestimated. In this aer, that amount is quantified. In the ast we have not accounted for the volume of measured free-sace consumed y the sored as comonent. By accountin for the volume consumed y the sored as comonent, the sace availale for free as is reduced. Examles show that this volume can e sinificant.

4 Bulk Comarison of Petrohysical Models Total Void Effective Void Bulk Total Void Free Gas Void Non-Clay Grain Non-Clay Grain Dry Clay Dry Clay Bound (Clay) Water Bound (Clay) Water Oranic Content Connected Pore Containin Free Oil, Gas, and Water Sored Gas Oranic Content Connected Pore Containin Free Oil, Gas, and Water Isolated Pore Isolated Pore

5 Old Petrohysical Model Bulk Total Void Effective Void Old etrohysical model Provided asis for calculatin volumes. Assumed free as orosity and oranics were indeendent. Bulk volume determined from mercury dislacement (V ). Grain volume determined from helium ycnometry (V ). S ( V V )( V V ) v S ( V V )( V V ) e ve v ve V V V V Non-Clay Grain Dry Clay Bound (Clay) Water Oranic Content Connected Pore Containin Free Oil, Gas, and Water G f (1 S B w ) Isolated Pore

6 New etrohysical model Bulk Total Void Free Gas Void Porosity for free-as and volume consumed y sored as is interconnected. Evidence has existed in the method used to measure adsortion isotherms. Un-corrected (raw) isotherms end downward. Sored volume must e accounted for in order to correct for this henomenon. This correction is called the Gis correction. Sored Gas Non-Clay Grain Dry Clay Bound (Clay) Water Oranic Content Connected Pore Containin Free Oil, Gas, and Water Isolated Pore

7 Simlified concetual model Old Methodoloy New Methodoloy Void sace measured y orosity measurement + Sored mass measured y adsortion exeriment = Total GIP Void sace measured y orosity measurement + Sored mass measured y adsortion exeriment - Free as volume taken u y sored as = Total GIP

8 Adsortion isotherm evidence Gis correction Storae Caacity (scf/ton) Sored Methane Storae Caacity Corrected Isotherm (Lanmuir) Raw Gis Isotherm Data Pressure (sia)

9 SEM evidence of lare ortion of orosity within the keroen

10 Free ore-sace correction G f ( Sw) B a a Mˆ s G sl L G f B (1 S w ) s 6 Mˆ G sl L

11 Sored hase density Previously ulished work all centers around /cm 3 for sored methane density. Duinin (1960) suested adsorate density related to van der Waals co-volume constant. Haydel and Koayashi (1976) reroduced co-volume constant value exerimentally. Menon (1968) suested the value was the liquid density. Other authors have had different theories, ut all are within the rane of /cm 3. Sored hase densities when fluid is aove the critical temerature are difficult. Difficult to searate the as from the sored hase.

12 Molecular dynamics simulation We took a molecular dynamics simulation aroach Utilizes rincials of Newtonian mechanics. Models fluid-solid, fluid-fluid interactions at ressure and temerature to determine values that are difficult to find exerimentally. Study effects on sored hase density ore-size temerature Molecular simulation cell consistin of rahite walls and OPLS-UA methane

13 Molecular dynamics calculated density rofiles damed oscillations

14 Sored hase density as a function of temerature

15 Examle of effects Tyical as shale Shale A: (low sortion caacity) Shale B: (hih sortion caacity) S w S o B M ˆ 20 l/l-mol 20 l/l-mol G sl 50 scf/ton 120 scf/ton 4000 sia 4000 sia T 180 o F 180 o F L 1150 sia 1800 sia 2.5 /cm /cm 3 s 0.37 /cm /cm 3 Shale A shows a decrease of 14.2% of free as and 11.6% of total as* Shale B shows a decrease of 30.2% of free as and 17.1% of total as* * Comared to old industry standard calculation methods

16 Conclusions and Future Work The disreard of the volume that is consumed y the sored hase in as shale leads to inadvertently hih values of total as-in-lace due to doule countin of the volume availale for free as. Evidence of a finite volume consumed y the sored hase has een around a lon time. It has een used to correct raw isotherm data. The sored hase mass is determined in the sored as exeriment. Proerly characterizin the sored hase density is critical in accountin for the volume consumed y the sored hase mass. A new method is shown to roerly account for this volume and remove it from the sace availale for free as. Future work in ulishin comositional effects on sored as quantities, takin the Lanmuir isotherm ortion of the equation and sustitutin a multi-comonent isotherm model. G f B (1 S w ) s 6 Mˆ G sl L