In the oil and gas industry, core analysis is a laboratory procedure for the determination of basic petrophysical properties of drilling cores to optimize production and maximize recovery. This study is carried out through the flow experiments on core samples taken from a petroleum reservoir. Special core analysis (SCAL or SPCAN) goes well beyond routine core analysis and provides a broad range of valuable data of reservoir formations such as relative permeability and capillary pressure.
A core is a cylinder-shaped sample of rock cut from the side of a drilled oil/gas well. Taken core from the well is cut up into multiple core plugs which are subsequently dried and tested.
In order to take a core sample, drilling must be stopped at the top of the reservoir. The drillbit is replaced by a rotary coring bit which has the cutting teeth and a hollow center. The cutting apparatus surrounds a hollow center where the core sample is stored. After taking the core sample from the well, the drillstring is pulled out of the hole and the core sample is retrieved.
Types of Cores
There are several types of cores, ranging in size from 1.75 to 5.25 inches in diameter and 20 to 400 feet in length, including full-diameter, native state, sidewall and oriented cores. The full-diameter core is the traditional core sample taken from a well which are typically restricted to carbonates and often contain fractures. Native state cores are bagged in order to keep all the reservoir fluids in the core under reservoir conditions. Sidewall coring is the cheaper and faster option to catch a core sampling, including retrieving variety of 1 to 1.75-inch core samples. Oriented cores are marked along the length of the sample with a groove to demonstrate the geographic/magnetic north.
Routine Core Analysis
The basic description, characterization, and simulation of reservoir come from routine analysis of core samples. It consists of measurement of porosity, saturation and permeability to analyze the three fundamental factors about a reservoir which include existence of fluid-filled spaces in the rock, existence of hydrocarbons in those spaces, and possibility of producing hydrocarbon fluids. Core computed tomography scans illustrate the core heterogeneity. Core gamma logging links the core depth to wellbore logging depth.
Core evaluation and measurement:
- Source Rock Analysis
- Special Core Analysis
- Core Gamma Log
- Core Photography
- Computed Tomography Scanning for Surface Analysis
- Grain Density
- Horizontal/Vertical Permeability
- Residual Saturations
- Connate Water
- Water Salinity
Special Core Analysis (SCAL)
Deep understanding of a reservoir estimates needs extra measurements acquired by the special core analysis (SCAL) to help petrophycist precisely define reservoir characteristics, improve reservoir simulation, and analyze formation damages. Subsequently, it assists geologists, reservoir engineers and drillers having better understanding of the well conditions and its potential productivity to optimize the long-time production and gainfulness of oil and gas fields.
Special core analysis (SCAL) measurement capabilities:
- Capillary Pressure
- Relative Permeability
- Steady and Unsteady state
- Wettability Determination
- Reservoir Condition Corefloods
- Improved Oil Recovery
- Petrophysical Correlation Measurements
- Core Geomechanics
- Pore Volume Compressibility
- Formation Damage Remediation
- Rock Fluid Sensitivity
- Mobile Fines Fluid Compatibility
- Mud Completion Fluid Damage
- Perforation Optimization
- Computed Tomography Scan Evaluation