Novel Procedure to improve Production Evaluation by using Effective Permeability with OFM
Joyce Plazas - Production Solutions Engineer
PEG-Data & Consulting Service - Las Morochas, Venezuela
This paper was prepared to be presented at the GFE controls in Houston. Mentors: Pablo Saavedra, Reservoir Engineer, MIP Champion, Eddie Martinez, West Venezuela DCSManager, and Claudio de la Cerda, DCS Operations Manager – VTT.
Production evaluation is an important part of the day to day operations of PEG-DCS. The effective permeability along with pressure and net pay are critical factors in determining the potential of a well. To solve the challenging problem of estimating effective permeabilitywhen there is not enough data available, a process based on current production and reservoir’s relative permeability – saturation relation was developed using the tool OFM. Also a correction factor “alpha” was defined to correct the relative permeability to oil when gas is produced along with water and oil, as is the case in many reservoirs for example lake Maracaibo, Venezuela. This process allowsa better understanding of the reservoir and improves risk mitigation for applicability of new technology and solutions to the client. Also this process adds value to the current PET methodology applied in training given in courses like TOP (Optimization Production Workshop) and advanced OFM training.
An important aspect of the service provided by PEG is validation of data,risk assessment and post-mortem evaluation of wells. This information helps the process of re-evaluation, improvement of procedures and applying the solutions that best solve the operational challenges of the area. The Oil Field Manager® (OFM*) is a suite of powerful modules for reservoir analysis and engineering processes known as Production Enhancement Technologies (PET). These processes helpunderstand and evaluate the production capabilities of the reservoir.
One of the challenges for drilling candidate evaluation is the lack of accurate data that jeopardizes the prediction of production expected from a well. One of the most important factors in determining the production potential for a well is the effective permeability along with the reservoir pressure andnet pay.
This project addresses the need to validate the permeability provided by the client. When there is not enough data available we can estimate the effective permeability with OFM by using production data and relative permeability curves.
In the reservoirs of interest for this study most zones are producing at pressures much lower than the bubble pressure. This allows the reservoir toaccumulate gas that is produced along with water and oil. Since the relative permeability curves available do not account for gas saturation, a correcting factor alpha is defined for estimating relative permeability to oil when there is three-phase flow system.
EFFECTIVE AND RELATIVE PERMEABILITY CONCEPTS.
One of the most important factors in determining the production potential for a wellis the permeability along with the reservoir pressure and net pay. There are different forms to express permeability: absolute permeability, effective permeability and relative permeability.
Absolute permeability of a rock, “K”, is defined as the permeability to a 100% saturating fluid that does not ‘react” with the mineral components of the rock4. It may be obtained from core test andPetrophysical correlations based on core data and wireline logs.
Effective permeability is a measure of the ability of the reservoir to conduct a fluid phase (Ko, Kg, & Kw) when the medium is saturated with more than one fluid5. Effective permeability can be obtained by petrophysical correlations from log data and well test data like Repeat Formation Tester (RFT), Modular Dynamic Tester (MDT),...