Since the 1980s, the number of horizontal wells has increased dramatically. As the flow regime is normally segregated, it is not possible to use conventional tools to obtain the production profile. More complex multiprobe or array tools are used, with distributed measurements around the cross section of the pipe.
Emeraude includes specific treatment for the Schlumberger PFCS, GHOST and FSI, the GE Sondex MAPS suite (CAT, RAT and SAT) and Hunter probe tools. Image views are created and cross sections displayed at any depth, and for any combination of passes. A regression process fits the discrete measurements with the relevant 2D models, contingent on user-defined constraints on segregation, phase presence or other tools. The output can be presented for QA/QC and results compared with the raw data. Average values of phase holdups, mixture velocity, and phase rates are produced and serve as inputs to the final interpretation.
Selective inflow performance (SIP)
In a multirate PLT, the well is logged at different surface rates. For each choke setting, the contribution of the zones and corresponding bottom hole pressures will change. Plotting the bottom hole flowing pressure versus the contributions for each zone, it is possible to obtain an IPR curve for each producing layer, and therefore quantify important reservoir parameters, such as reservoir pressure, productivity index and absolute open flow.
In Emeraude, an SIP analysis can be made with a few clicks. Pseudopressures can be used for gas. An unlimited number of SIP’s can be created and compared. Each zone can be assigned a different model: straight line, C&n or L.I.T. The SIP can use the total rate, a phase rate or the total liquid rate. Data may be downhole or from surface. Pressure datum correction and composite IPR’s are available.
Increasingly, wells are completed with fibre optic distributed temperature sensors (DTS). Even in a conventional PL job, the spinner may fail or give an erroneous response under certain circumstances (counter current, high viscosity etc). In such a case the temperature log may be the only source of information about the rates. If the thermal properties of the fluids, completion and formation are known, and if the problem is not undetermined, it may be possible to infer the production profile based on the temperature log.
Emeraude offers a segmented model and an energy model. The analytical segmented model accounts for enthalpy balance in front of inflow zones, and conduction/convection between zones. Joule-Thomson effects are calculated from a user estimated pressure drop. The numerical energy model solves the full energy equation in the wellbore and the reservoir, accounting explicitly for the thermal effects within the reservoir.
When designing a steam injection well, the goal is to obtain the highest quality of steam downhole. That is, to minimize the condensation of liquid water and maximize the volume of vapour that the perforations receive. The variables that can be optimized are the injected rates, pressures and thermal properties of the completion.
This special analysis uses a dedicated 2-phase steam-water PVT for the design of steam-injection tests. The temperature, pressure, holdup and velocity profiles are calculated from surface, to determine the property of the injected fluid in each zone. Relevant slip models are considered.
Apparent permeability (APERM)
Estimation of effective permeability at reservoir scale is fundamental for an accurate reservoir model. In carbonates, the permeability in vuggy or fractured intervals can be dramatically different from the matrix permeability measured in core plugs. The apparent permeability based on PLT data may be the solution for a field-scale characterization.
This method corrects, with the PL interpretation, the open-hole effective permeability. It uses an IPR relationship where the relevant reservoir or perforation parameters are defined zone by zone. The method is implemented for single-phase liquid, liquid mixture, or for gas using pseudopressures.
Leaks represent an extremely dangerous situation for the integrity of the well. Leak diagnostic is normally performed through the use of callipers, spinners and temperature. For very small leaks, the spinner may have insufficient resolution to identify the leak. It may also be missed by the caliper. However, temperature is very sensitive and can provide and easy method to determine the presence of leaks.
The leak option simulates the thermal profile along the tubing and annulus in cases where a tubing leak is suspected. An extra energy equation is added to the system that accounts for energy conservation in the annulus. The balance of energy is then made between tubing flow and annulus flow (accounting for conductive and convective heat fluxes) and in between annulus flow and the reservoir (accounting for conductive heat fluxes).