CO2 storage in gas-bearing shales of the Baltic basin

Transcription

1 CO2 storage in gas-bearing shales of the Baltic basin Marek JAROSIŃSKI, Adam WÓJCICKI PGI-NRI EERA Birmingham,

2 SHALESEQ project and its goals PHYSICO-CHEMICAL EFFECTS OF CO2 SEQUESTRATION IN THE POMERANIAN GAS- BEARING SHALES ( ) Developing a multi-scale model of CO2 sequestration in shale formations combined with simultaneous stimulation of natural gas production....understanding the underlying mechano-chemical processes governing CO2 behavior in shale formations... contribute to characterize the mechanisms of permanent storage of CO2 in shales. CO2 has a substantially higher sorption capacity than methane to the organic matter contained in shales. CO2 may therefore be used to enhance shale gas production, as the secondary method, while at the same time remaining trapped in the shale matrix. The assessment of the CO2 storage capacity is not directly mentioned in the Project scope, however it can make a good platform of the ShaleSeq results integration

3 Shale gas and oil resources world-wide after eia.gov, 2015 The development of unconventional hydrocarbon resources has changed the energy-political landscape of the world (actually North America, recently China) and could provide economic and safe solutions for the future energy supply in Europe (?).

4 Shale gas and oil exploration in Poland Till now 74 exploratory wells for unconventional hydrocarbon reservoirs (some of them also for conventionals), including 18 directional/horizontal wells. Hydraulic fracturing has been performed in 28 vertical and directional/horizontal wells. Test results from a few wells suggest a possible gas production of about 10% to 30% of the commercially sustainable level. The most prospective area is the Baltic basin (northern Poland/Pomerania.

5 SeqWell new POGC(PGNiG) B-1 well The study is mostly (not exclusively) based on data from that well.

6 Location (maturity map PGI-NRI, 2012 report) Dry Gas Wet Gas + Oil P O M E R A N I A SeqWell depth (Silurian/Ordovician) ~3,5 km; reservoir pressure ~36 MPa reservoir temperature >85 C The old maturity map is incorrect - new data changed the picture dramatically - wet gas zone shifts towards W/SW, covering the well in question.

7 Accumulation spaces for natural gas in shales after Dyrka, in: Sidorczuk et al., 2013 Gas adsorbed and diffused in nanopores in organic matter

8 Shale gas production In course of production a change of the ratio: (interpore+fracture gas)/(desorbed gas) can be observed. After 10 years the share of free gas decreases significantly and dominance of desorbed gas can be observed. Then CO2 injection could be used as a secondary method to gas recovery, similarly to CO2-ECBMR (CO2-CH4 replacement). Shi et al., 2005 after 10 years of production dominance of sorbed gas after Godec, 2013

9 Static vs dynamic CO2 storage capacity The dynamic CO2 storage model has to cover: Flows and diffusion matching the dynamic reservoir model (i.e. production history); A good deal & quality of (trustworthy) data to calibrate the porosity structure and permeability models in reservoir-scale (???); One is not able to make a robust dynamic assessment without CH4 production data. If you are not able to construct a dynamic reservoir model... Construct the static CO2 storage model only - In the static model flowrates, processes and transport routes are neglected - It is assumed that CO2 reaches somehow a permanent storage space

10 CO2 injection scenario for dynamic assessment Preferential scenario of CO2 injection into shale reservoir (an example after Kalantari-Dahaghi et al., 2010). Assuming 1 km2 assessment unit area we need a few wells.

11 Components of the static CO2 storage capacity assessment Adsorption capacity (mostly on dry organic nanopores, inorganic adsorption on illite grains partly blocked by presence of capillary and ireducible water; CO2-CH4 replacement ratio 2-6 x - Kang et al., 2011; Heller & Zoback, 2014; good, positive correlation with TOC) Pore space in shale matrix (macropores > 20 nm predominantly free gas, mezopores 5-20 nm, micropores 2-5 nm predominantly adsorbed gas; Kang et al., 2011) Fracture space (natural & technological) Threshold values of input parameters (TOC, thickness, brittleness ) for storage complex are necessary.

12 Sorption capacity and storage potential of shales Volume [Bcm] Mass [Mt] Adsorbed CO Free CO Total CO As above 10% storage efficiency Total CO 2 /1km 2 0,56 1,12 10% storage efficiency 0,05 0,112 Tao i Clarens, 2013 Sorption characteristics of CH4 and CO2 compiled from a variety of published sources CO2 storage capacity of the entire Marcellus shale play (~ km2; 20 years of storage), after Godec et al The effective storage capacity (storage efficiency coefficient -10%) corresponds to storage potential in saline aquifers of Poland.

13 Input data (POGC wells, mainly SeqWell) Sorption capacity (a function of Langmuir volume & pressure and reservoir pressure) of shale rock [m3/t]. Bulk density of shale rock. Net thickness of shale reservoir (based on TOC, porosity filled with hydrocarbons, gas content, quartz+carbonate and clay content)*. Total values and distribution of effective porosity (classes of pores/fractures: 3-10 nm (predominantly adsorbed gas), nm, nm, >1000 nm). Gas expansion ratio (free gas). *based on both laboratory analyses and well logging data interpretation

14 Input data Example of well logging interpretation (porosity) used to determine net thickness of shale reservoirs (ShaleSeq: M. Roman, 2016). Sasino formation, Jantar member of Pasłęk formation and, to a lesser extent, lower part of (Wenlockian) Pelplin formation are prospective shale reservoirs there.

15 The assessment (adsorbed gas) Synthetic static model of the unit area (1 km 2 ) based (mostly) on data from POGC/PGNiG SeqWell, and other wells in the vicinity. The complexes of TOC>1.5%, gas filled porosity >2%, gas content >0.5 m 3 /t, quartz&carbonate content > 40% were considered A simple formula for adsorbed gas GIPa: GIPa=V ρ G (Ladage & Berner, 2012) was used and the (theoretical) CO2 storage capacity in shales is: GIPa x CO2/CH4 ratio where V is reservoir rock volume, ρ bulk density and G sorption capacity. Formation /member Stratigraphy thickness [m] average TOC [%wt] net reservoir thickness [m] Sorption capacity G [m3/t] bulk density CO2/CH4 ratio*** Pelplin1 lower Wenlock 67 0,8 20±2 0,80±0,16 2,60±0,02 2,53±0,51 (upper & middle) Pasłęk(Jantar) Llandowery Jantar (basal) Llandowery 13 3,2 13,0±1,3 1,40±0,28 2,45±0,02 3,76±0,75 Prabuty Ashgill 7 0,5 0 Sasino Caradoc (+Llanwirn) 15 2,5 10±1 1,60±0,32 2,48±0,02 2,60±0,5 ***CO2/CH4 ratio - ShaleSeq: Lutyński & Gonzalez, 2015

16 The assessment (adsorbed gas) Monte Carlo method was applied assuming tentative uncertainity ranges: ±10% in case of net reservoir thickness, ± 20% - sorption capacity & CO2/CH4 ratio, and a fixed value of ± 0.02 g/ccm was assumed in case of bulk density. The following estimations of the (theoretical) CO2 storage capacity in 1 km2 unit area of Polish Baltic basin were obtained: Formation /member Stratigraphy minimum (P10) [Bcm] median (P50)[Bcm] average [Bcm] maximum (P90)[Bcm] Pelplin1 lower Wenlock 0,004 0,041 0,042 0,096 Jantar (basal) Llandowery 0,001 0,041 0,042 0,093 Sasino Caradoc (+Llanwirn) 0,003 0,039 0,04 0,089 TOTAL - 0,121 The median of total (theoretical) CO2 storage capacity of Llandovery- Ordovician complex is Bcm/km2 or 0.24 Mt/km2. Assuming 10% storage efficiency we got effective storage capacity Mt/km2 (a pilot project). CO2 sorption capacity per tonne of shale varies from 0.5 kg CO2/t (lower Wenlock) to 2.4 kg CO2/t (basal Llandowery).

17 Conclusions Shales in Polish Baltic basin do not have such good parameters as Marcellus shale that is reason not only basal Llandowery and Caradoc shales of relatively high TOC (but of small net thickness) but also mediocre shales of lower Wenlock have been considered in the study. As a result, the assumed total thickness is similar as Marcellus productive shales (about 40 m) but only the CO2 sorption capacity of the Jantar/basal Llandowery matches the corresponding parameter of Marcellus (in our case the storage capacity is likely 3 times lower than in the US). Till now no commercial production in the area in question was achieved most likely because of low frackability (relatively high content of clay minerals), the lack of overpressure and, last but not the least, the fact Polish shales are located considerably deeper than their US counterparts. The study is devoted to some aspects of enhanced recovery of shale gas AFTER meaningful gas production from shale reservoirs. At this moment that is a purely theoretical exercise.

18 Thank you for your attention: