Cased Hole Coal Bed Methane Measurements Written by Hermann Kramer

Transcription

1 Cased Hole Coal Bed Methane Measurements Written by Hermann Kramer

2 Introduction This talk will discuss learning's from both Hotwell Canada and Roke Technologies. Roke Technologies is the continuation of the original company Roke Oil Enterprises which was founded in Roke specialized in providing mining (coal) and geotechnical logging and measurement services and was once regarded as the best mining measurement company available in Canada. Hotwell Canada and Roke have been working together over the past 2 ½ years.

3 A Starting Point Before we can compare logging measurements of CBM, we need to understand: Logging Measurements The physics of the measurements The tools that make the measurements Data limitations The models that the measurements are based on Characteristics of CBM Characteristics of Coal as related to the measurement Characteristics of CBM as related to the measurement

4 Characteristics of Coal Coal is a complex combination of materials, and the combination can greatly differ from one formation or deposit to another. In addition to carbon, coals contain hydrogen, oxygen, nitrogen and varying amounts of sulphur. Alberta coals are comparatively low in sulphur, ranging from 0.2 to 0.7 percent. Coals can have impurities Ash Coal has a low density gm/cc Open hole density tools were not designed for this low of a density therefore errors occur in the measurements Water can move easily thru coal Coals tend to break out when drilled This leads to washouts at coal seams which causes errors in certain types of measurements

5 Characteristics of Coal Bed Methane Coal bed methane (CBM) is simply methane found in coal seams. CBM is generated either from a biological process as a result of microbial action or from a thermal process as a result of increasing heat with depth of the coal. Coal seams can be saturated with water, while methane is held in the coal matrix by water pressure Methane is released when the pressure holding the methane in the coal is release. The CBM is in an oil state under the extreme molecular pressures of the coal matrix.

6 Measurement Models Best measurements are obtained in-situ. Examples of in-situ measurements include well logs and drill stem tests (reservoir temp / pressure). Examples of non in-situ measurements include core data and cuttings analysis Measurement devices need to be designed for the in-situ environment. Examples of in-situ environments include open hole wells and cased hole production wells. For CBM - Theoretical predictions were not met with traditional models, therefore a new model was developed that gave better correlation between theoretical and actual results.

7 Roke s Experience with Coal Purchased conventional style logging tools (density, neutron, resistivity, gr) and started logging in Coal mines in 1972 Observed that measurement devices had high error. Redesigned the logging tools. Observed that traditional models did not work. Developed the coal water ash model to give better predicted results Presented technical paper October 1977 at CWLS Continued working in the Coal mining industry until early 1980 s Miner s have different objectives with Coal than the CBM producers How much coal can I mine? How much ash can I expect? How much water is there? How many canaries do I need?

8 Roke s In-Situ Coal Water Ash Model COAL MATTER COAL = WATER WET ASH

9 CWAM Coal Water Ash Methane COAL MATTER COAL = METHANE WATER WET ASH

10 CWAM - Coal Water Ash Methane Model Based on similar principals as the CWA model Cleat porosity 1 3% of coal porosity Maximum Micro porosity ~24% Total Maximum theoretical coal porosity = 27% Throat opening on Micro porosity pores widens during production as coal fines continue to be produced along with CBM. In-situ CBM exists in oil state under pressure ~0.5g/cc Gas Oil Water contacts exist in CBM coals

11 COAL, OIL, ASH No Permeability

12 COAL, OIL, WATER, ASH

13 COAL, OIL, FREE GAS, ASH

14 COAL, OIL, FREE GAS, ASH

15 COAL, WATER, ASH

16 Our Measurement Experience

17 Hotwell Canada s PNN Started logging CBM in Initial results indicated that methane production was related to Ratio Porosity curve. Coal seams were sometimes missed because not all coals had clean gamma ray. R&D work was halted early 2007.

18 CBM and Bypassed Pay Purpose; to evaluate the already producing well for coals and bypassed conventional zones. The coal seams were clearly flagged using standard gamma ray and porosity data, Bypassed pay was also identified that was missed by the original open hole evaluation.

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21 Roke Quad Neutron Designed for cased hole in-situ environment Designed to measure porosity and identify hydrocarbons. First run in coal wells in Led to realization of liquid methane in coal matrix.

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23 Summary Cased Hole evaluations can be done effectively to monitor coal bed methane reservoirs. There appears to be a direct correlation between nuclear response and production

24 Thank You.