FRACTURE RESERVOIR CHARACTERIZATION BY FIBER-OPTIC DISTRIBUTED TEMPERATURE LOG
One of the important features of the fiber-optic distributed temperature log is its ability to acquire continuous, instantaneous and simultaneous temperature profile along the entire wellbore. Series of successive temperature profiles sampled every one minute or so enable to analyze transient temperature phenomena, which may pertain to important reservoir properties. For example, when change of rate occurred to the fluid flow such as due to water injection, the temperature profile over the section exhibits transient phenomena associated with the fluid flow. The characteristics of the phenomena depend on several factors including the flow profile which itself exhibits transient nature depending on fluid compressibility, permeability and reservoir extent, the original temperature profile, the temperature of injected fluid and that of the reservoir fluid flowing into the wellbore, the degree of rate alteration, well geometry, flow regime and etc.
Afterflow Measurement and Deconvolution in Well Test Analysis
The introduction of new production logging devices which simultaneously measure and record bottom-hole flow and pressure allows improved identification of reservoir parameters from well test analysis. In particular the detection of sandface flow resulting from the location of the logging tool just above the formation top means that the actual mechanics of wellbore storage phenomena can be excluded from consideration. In the case of pressure buildup or falloff tests the afterflow is directly measured and the amount of information available for interpretation at early time is essentially doubled in comparison to the situation where only pressure is recorded and flow is deduced from a simplified model based on a constant wellbore storage coefficient. The monitoring device continuously transmits the instantaneous pressure and sandface flowrate throughout the test and methods of well test analysis for a general, known rate schedule are considered. The deconvolution method is based on homogeneous, radial flow theory and its performance when applied to simultaneous, transient pressure and flow data from heterogeneous systems is considered. It is shown that in the case of drawdown in which the rate schedule is monatonic the variable-rate semilog plot based on homogeneous deconvolution exhibits the same characteristics as the constant-rate semilogmore » plot. This is demonstrated for two types of heterogeneity.« less
Long-range 1.5 μm OTDR in a single-mode fibre using A D 2 gas-in-glass laser (100 km) or a semiconductor laser (60 km)
We have observed Rayleigh backscatter in a single-mode fibre in optical time domain refiectometry at 1.56 μm wavelength to a range of 100 km using a D 2 gas-in-glass laser, and to 60 km at 1.53 μm using an injection laser. The low-noise receiver used an InGaAs PIN photodiode and a FET-input operational amplifier with averaging of 1000 times to provide signal/noise enhancement.