ROCK PROPERTIES

RESERVOIR
1. porous geological formation
2. pore space water+HC
3. eg: limestone, sandstone, dolomite
4. behavior determined by
  1. gravitational force (density)
  2. capillary force (fluid climb up surface)
5. requires a porous media
Tests
1. routine core analysis
  1. Poro, Permea, saturation
2. special tests
  1. press, wettability,tension
POROSITY
1. ratio of pore space:bulk volume
  1. good reser. :15-20% poro. Poor: 5-10%
2. Types
  1. Primary (deposition)
  2. Secondary (changes: faults, fracture, cement)
3. Cal.
  1. HC porosity
  2. Total/absolute poro
  3. Effective Poro
    1. only inter-connected pore (not incl. trapped pore)
4. Influenced by
  1. large grain size/shape/ narrow dist. (same size grains) (inc.)
  2. sorting & angularity packing (inc.)
  3. compaction (press, depth) decre.
  4. chemical sol (decrease), fracturing (inc.)
5. Measured by
  1. core scale
    1. effective poro: fluid inject, extract mass
    2. weight method
    3. Helium Porosimeter (press)
  2. log
    1. >difficult,$$$, usually run to measure many properties at once
  3. Production performance
    1. data from reser. production over years
6. define rock ability to store fluid, void fraction
7. produce ISO-POROSITY map of reser.
CONSOLIDATED (lose grain) vs. UNCONSOLIDATED (cement/chemical stick rock together)
1. Gravel, sand, silt, clay vs. basalt, shale, lime/sandstone
FLUID SATURATION
1. fraction of pore vol. occupied by that fluid
2. during production S(oil/gas) decr., S(water) inc.
PEMEABILITY - HYDRAULIC CONDUCTIVITY
1. absolute permea
  1. capacity to transport fluid through pores
  2. large regular grains (decr. SA, friction) inc. pemea
  3. exist of another phase, clay/cement form. decr. pemea
  4. fracture readily incr. pemea
  5. KLINKENBERG effect variate pemea
2. CONVENTIONAL (sandstone->gravel)
3. UNCONVENTIONAL (shale)
4. PARAMETERS
  1. Average velocity (discharge Q)
  2. Interstitial velocity (linear v or pore v)
  3. Hydraulic gradient: ratio change height:length of sand pack
  4. Potential gradient: ratio change poro: length of sand pack
5. measured by: Core flood test (inject fluid), well test (cal. from flow, press)
a rock property independent of position within porous medium
1. HOMOGENOUS medium
a rock property independent of direction within porous medium
1. ISOTROPIC medium
a rock property vary at a point of porous medium
1. ANISOTROPIC medium
COMPRESSIBILITY
1. change in vol. (rock, pore, fluid) in press
2. during production: press decr.- rock bulk vol. decr.- grains expand -pore vol. decr. (poro)
3. Formation compressibility
  1. equal to pore compressibility
RESISTIVITY
1. electrical properties
2. depend on void, fluid type, salinity, temp, poro, pore geometry, form. stress, rock composition

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ROCK PROPERTIES

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