GATE Petroleum Engineering Latest trends in Petroleum Engineering Syllabus

Latest trends in Petroleum Engineering syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Latest trends in Petroleum Engineering in GATE Petroleum Engineering, not a summary of it.

1. 1

   Coal bed methane

   1 topic

   • Introduction to Coal bed methane
2. 2

   Shale gas

   1 topic

   • Overview of Shale gas
3. 3

   Oil shale

   1 topic

   • Exploration and Extraction of Oil shale
4. 4

   Gas hydrate

   1 topic

   • Formation and Properties of Gas hydrate
5. 5

   Heavy oil

   1 topic

   • Characteristics and Processing of Heavy oil

Latest trends in Petroleum Engineering flashcards for GATE Petroleum Engineering

19 of 50 cards from the Latest trends in Petroleum Engineering deck — real questions with worked answers.

1. What is Coal Bed Methane (CBM)?

   Coal Bed Methane is natural gas (predominantly methane, $\ce{CH4}$) that is adsorbed onto the internal surfaces of coal seams and stored within the micropores of the coal matrix, generated during the coalification process.

2. By what mechanism is methane primarily stored in coal seams, unlike conventional gas reservoirs?

   It is stored mainly by adsorption onto the internal surface of the coal matrix (not as free gas in pore space). A typical coal can hold 6-7 times more gas by adsorption than an equivalent conventional reservoir of the same volume.

3. What adsorption model describes the relationship between methane content and reservoir pressure in coal?

   The Langmuir isotherm, given by $V = \frac{V_L \, P}{P_L + P}$, where $V_L$ is the Langmuir volume (maximum adsorption capacity) and $P_L$ is the Langmuir pressure at which adsorbed volume equals $\frac{V_L}{2}$.

4. What is the typical sequence of fluid production phases during CBM (dewatering) recovery?

   (1) Dewatering/single-phase water flow stage — water is pumped to lower pressure; (2) Two-phase flow stage — gas desorbs and is produced with declining water; (3) Single-phase gas-dominated stage with peak then declining gas production.

5. Why must water be pumped out (dewatering) before significant gas is produced from a CBM well?

   Coal seams are initially water-saturated and gas is held by adsorption proportional to pressure. Removing water lowers the reservoir pressure below the desorption (critical desorption) pressure, allowing adsorbed methane to release from the coal matrix.

6. What two natural fracture/porosity systems make up the dual-porosity structure of coal?

   The cleat system (natural fracture network providing permeability) and the coal matrix micropores (where gas is stored by adsorption). Cleats consist of face cleats (continuous, primary) and butt cleats (discontinuous, perpendicular).

7. Distinguish face cleats from butt cleats in coal.

   Face cleats are the dominant, continuous, through-going fractures that control the primary permeability direction; butt cleats are shorter, discontinuous fractures oriented roughly perpendicular to face cleats and terminate against them.

8. What is the critical desorption pressure in CBM?

   The reservoir pressure at which the coal becomes saturated with respect to its adsorbed gas content, so that any further pressure reduction causes methane to begin desorbing from the coal matrix.

9. What is the difference between thermogenic and biogenic coal bed methane?

   Thermogenic CBM is generated by heat and pressure during coalification at higher ranks/temperatures; biogenic CBM is produced by microbial (methanogen) activity, either early (during peat formation) or late stage (from meteoric water introducing microbes).

10. How does permeability of a coal seam typically change as CBM production proceeds, and why?

    Permeability often increases over time due to matrix shrinkage: as methane desorbs, the coal matrix shrinks, widening the cleats. This counteracts the cleat-closing effect of increasing effective stress as pore pressure drops.

11. What is shale gas?

    Shale gas is natural gas trapped within fine-grained, organic-rich sedimentary shale (mudstone) formations, where the shale acts simultaneously as the source rock, reservoir rock, and seal.

12. In what forms is gas stored within a gas shale?

    (1) Free gas in the natural fractures and matrix pore space; (2) Adsorbed gas on the surface of organic matter (kerogen) and clay minerals; and (3) a minor portion dissolved in liquid hydrocarbons and formation water.

13. Why does shale gas require hydraulic fracturing and horizontal drilling for economic production?

    Shale has extremely low matrix permeability (nano-darcy range), so gas cannot flow naturally. Horizontal wells maximize contact with the thin reservoir, and hydraulic fracturing creates artificial fracture networks to provide flow pathways.

14. What is TOC and why is it a key parameter for shale gas evaluation?

    TOC is Total Organic Carbon, the weight percent of organic carbon in the rock. It indicates the source/storage richness; higher TOC means more kerogen for gas generation and adsorption. A TOC of roughly $> 2\%$ is generally considered favorable for a productive gas shale.

15. What is thermal maturity (vitrinite reflectance $R_o$) and what range indicates the dry gas window for shale?

    Thermal maturity measures how far source-rock kerogen has been converted to hydrocarbons, quantified by vitrinite reflectance $R_o$. The dry gas window typically corresponds to $R_o > 1.4\%$ (oil window roughly $0.6\%$–$1.0\%$, wet gas/condensate $\approx 1.0\%$–$1.4\%$).

16. What is brittleness in shale gas reservoirs and why is it important?

    Brittleness is the rock's tendency to fracture rather than deform plastically; it is favored by high quartz/carbonate and low clay content. Brittle shales fracture more effectively (creating complex fracture networks) during hydraulic stimulation, improving productivity.

17. What are the main components of hydraulic fracturing fluid used in shale gas wells?

    Approximately 90% water, about 9% proppant (typically sand or ceramic beads to hold fractures open), and about 1% chemical additives (friction reducers, gelling agents, biocides, surfactants, scale inhibitors).

18. What is the role of proppant in hydraulic fracturing?

    Proppant (sand or ceramic particles) is carried into the induced fractures by the frac fluid and remains there after pressure is released, propping the fractures open to maintain conductive flow paths for gas to reach the wellbore.

19. Why do shale gas wells exhibit very steep initial production decline?

    Initial high rates come from free gas in the stimulated fracture network, which depletes quickly. Subsequent production depends on slow desorption and ultra-low-permeability matrix flow, causing a sharp decline (often 60-80% in the first year) followed by a long, low-rate tail.

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