SCALE HETROGENEITY AND ITS IMPACT ON RESERVOIR CHARACTERISATION AND EVALUATION DATA FROM DIFFERENT SCALES USED IN RESERVOIR EVALUATION AND CHARACTERISATION Reservoir Scale Pore Scale Standard/ HighTech Logs Conventional Core Analysis/ Special Core Analysis µCT XRD SEM Seismic Dye Test/ Tracer Study FMI µmt 0.1 mm cm mt 102
Download ReportTranscript SCALE HETROGENEITY AND ITS IMPACT ON RESERVOIR CHARACTERISATION AND EVALUATION DATA FROM DIFFERENT SCALES USED IN RESERVOIR EVALUATION AND CHARACTERISATION Reservoir Scale Pore Scale Standard/ HighTech Logs Conventional Core Analysis/ Special Core Analysis µCT XRD SEM Seismic Dye Test/ Tracer Study FMI µmt 0.1 mm cm mt 102
SCALE HETROGENEITY AND ITS IMPACT ON RESERVOIR CHARACTERISATION AND EVALUATION DATA FROM DIFFERENT SCALES USED IN RESERVOIR EVALUATION AND CHARACTERISATION Reservoir Scale Pore Scale Standard/ HighTech Logs Conventional Core Analysis/ Special Core Analysis µCT XRD SEM Seismic Dye Test/ Tracer Study FMI µmt 0.1 mm cm mt 102 mt 104 mt 106mt 25 kms Skeleton formation during pillar gridding 7 million Grid cells Cell size: 200m x 200m Geological Model 25 kms Porosity Model Fig 12 Cross section view of porosity (E-W) Saturation Model TYPES OF SEDIMENTARY ROCKS Clastic rocks • • • • Chemical & Organic rocks Sandstones Conglomerates Breccia Shale/mudstones Carbonate rocks Organic rocks Evaporitic rocks These rocks are formed due to evaporation of saline water (sea water) eg. Gypsum, Halit (rock salt) Form basically from CaCO3 – both by chemical leaching and by organic source (biochemical) eg. Limestone; dolomite Form due to decomposition of organic remains under temperature and pressure eg. Coal/Lignite etc. CLASTIC ROCKS • formed from broken rock fragments weathered and eroded by river, glacier, wind and sea waves. These clastic sediments are found deposited on floodplains, beaches, in desert and on the sea floors. solidify Clastic rocks • Clastic rocks are classified on the basis of the grain size: conglomerate, sandstone, shale etc. CARBONATE ROCKS • Limestone: It is a non-clastic rock formed either chemically or due to precipitation of calcite (CaCO3) from organisms usually (shell). These remains will result in formation of a limestone. • Limestones formed by chemical precipitation are usually fine grained, whereas, in case of organic limestone the grain size vary depending upon the type of organism responsible for the formation – Chalk: which is made up of foraminefera is very fine grained – Fossiliferous Limestone: which medium to coarse grained, as it is formed out of cementation of Shells. ASPECTS SANDSTONE CARBONATES Amount of Primary Porosity in sediments Commonly 25-40 % Commonly 40-70% Amount 0f ultimate porosity in rocks Commonly half or more of initial porosity. 15-30% in common Commonly none or a small fraction of initial porosity: 515 % common in reservoir facies. Type of Primary porosity Exclusively interparticle Interparticle predominates but intraparticle and others are important. Type of Ultimate porosity Exclusively primary interparticle Widely varied because of post depositional modifications Sizes of pores Diameter and Throat sizes closely related to sedimentary particle size and sorting. Diameter and throat sizes commonly show little relation to sedimentary particle size or sorting. Shape of pores Strong dependence on particle shape. Greatly varied ranges from strongly dependent to completely independent of shapes of particles.. ASPECTS SANDSTONE CARBONATES Uniformity of size,shape and distribution Fairly uniform within a homogeneous body. Variable, ranging from fairly uniform to extremely heterogeneous even within the body make up of a single rock. Influence of Diagenesis Minor: Usually minor reduction of primary porosity by compaction and cementation. Major:can create, obliterate or completely modify porosity. Cementation and solution important Influence of fracturing Generally not of much importance in reservoir properties. Of major importance in reservoir properties if present. Permeability –Porosity relationship Relatively consistent; commonly dependent on particle size and sorting Greatly Varied: commonly independent of particle size and sorting. CARBONATE HETEROGENITY & CALE VARIANCE OF PROPERTI MASSIVE SAND DEPOSITES ON THE BANKS OF BRAHAMAPUTRA Mammoth Cave National Park, Kentucky boasts the world's longest cave system—more than 365 miles (587 kilometers) have been explored so far. Formed within a Massive Carbonate Layer with a clastic caprock. CARBONATE POROSITY TYPES Intergranular Intercrystalline Moldic Moldic Fenestral Shelter Fracture Vugs Clastic vs Carbonate WELL : D-1-I5 Plug : 23 PHI : 25.1 % Kair : 44.01 md Plug : 24 PHI : 17.1 % Kair : 0.37 md ~ A 100 times Difference in Permeability with no visible difference in log characters. Petrophysical data from the work of D.C.Tiwari etal . IRS Permeability Vs Porosity (Core – Derived) Field: D-1 Prof. Larry Lake, Head, Dept. of Petroleum Eng. University of Texas, Austin Querry: Homogeneity and Isotropic properties in Geological systems are SCALE dependent. These properties have a meaning only when we define the scale of operation with its boundary conditions. In carbonates for example, the permeability in core scale vary wildly. Different core plugs from the same core have wide scatter in their permeability values. This is manifestation of extreme heterogeneity of a physical property in micro scale. But the same carbonate in reservoir scale, indicates flow behavior which shows patterns of uniformity. The observable pressure drop in a well due to production from another well kilometers away is remarkable in carbonates. Answer: Yes. I also agree. In carbonates the local properties vary widely but things are more predictable at a larger scale. I also agree that petrophysical properties are scale dependent. I have a research project going on about this right now. It is not just a carbonate issue. It is always easier to predict things in aggregate than individually. LIMITS OF MEASUREMENT & DISTRIBUTIVE NATURE OF PROPERTIES All tools measure an average property of a medium limited to the tool resolution. In Logging the tool resolution is related to two basic factors: - Vertical Resolution - Depth of Investigation These two parameters define the size of the volume for sampling Halliburton Neutron Vertical Resolution Depth of Investigati on CNT Too l 24 inch es 8-12 inch es Schlumberger Neutron Vertical Resolution Depth of Investigation CNT Too l 24 inch es 9-12 inch es CNT Tool Enhanced 12 inches 9-12 inches Tool Response of Neutron Tool Vertical Resolution 24” = 60 cm Approximate volume scanned for each observation : π r2h ~ 1.7x105 cm3 Depth of Investigation 12”=30 cm Each observation provides the average property of a cylindrical volume of approximately 105 cm3. Core Plug A : Has Matrix as well as Fracture and some Vugular Porosity Core Plug B: Has only Matrix component of Porosity Log Reads the average property of the Volume of investigation, whereas both the cores will read quite different values for a given property. Fundamental Issues • Support and stationarity PORES POROUS MEDIA Property Volume Microscopic Macroscopic (After Bear, 1968, Halvorsen, 1986) Log μCT Core Plug Ф 20 25 21 15 12 23 Ф=22% 18 16 08 15 20 meter cm μm Probe permeametry Multi-tip volume experiment SIDE 1 10000 1 1 0.01 0.01 SIDE 2 10000 100 100 1 1 0.01 0.01 Small tip 10000 Non Stationarity 100 Large tip 1 4 3 2 1 0 Depth, cm 100 1 0.01 Depth, cm Corbett, Anggraeni and Bowen, Log Analyst 1999 12 1 S mall tip 8 100 SIDE 4 10000 6 Permeability, mD SIDE 4 10000 0.01 Large tip 0.01 10 SIDE 3 4 1 0.01 Poor support SIDE 3 10000 100 Permeability, mD Stationarity SIDE 2 10000 2 Good support 100 0 Sst 100 Lst SIDE 1 10000 Cubic Hassler cell Upscaling Experiment SIDE 1 10000 Poor support 100 1 0.01 SIDE 2 1 0.01 10000 10000 100 100 1 1 0.01 0.01 SIDE 3 10000 Upscalable? 100 100 1 1 SIDE 3 0.01 1 SIDE 4 1 0.01 4 2 1 0 Depth, cm 3 0.01 100 Corbett, Anggraeni and Bowen, Log Analyst 1999 Depth, cm 12 100 10 10000 SIDE 4 10000 8 Permeability, mD CUBES 6 0.01 Permeability, mD CUBES 10000 4 Upscalable SIDE 2 2 Isotropic 100 0 Good support SIDE 1 10000 Scale Definitions… Quinland and Ewers, 1994 K (m/s) Hydraulic Conductivity Permeability Scale Effect... Basins 10-2 10-4 Effect of karst dissolution Bed Laboratory Effect of macrofractures 10-6 10-8 10-1 Effect of pores and microfractures 100 101 102 103 104 Scale (m) Kiraly (1979) PERFORMANCE vs. PREDICTION 35.00 Field Performance Qg Mmm3/d 30.00 1996-Prediction 25.00 2005-Prediction 20.00 15.00 10.00 5.00 0.00 0 5 10 15 years 20 25 ‘Mukta’ BCM ‘BASSEIN’BCM Year Total-BCM 34 239 2004 273 34 268 2007 302 41 268 2009 310 41 288 2010 330 Full Core Core Sliced along length Symmetric Features (Planar Symmetry) Non Symmetric (Planner Asymmetry) WHOLE CORE PIECE SHOWING ABUNDANT PRESENCE OF VUGS AND FRACTURES ALONG WITH GOOD PRIMARY MATRIX POROSITY. Whole Diameter Core Matrix Fractures Vugs Triple Porosity System Sectioned Core Time slice at 1920msec from Dip Volume attribute Fig:24