Triple Phase Formation Fluid Evaluation Using Pulsed-Neutron Tools
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Solution Overview
Problem
Current well drilling methods for oil and gas exploration face challenges in accurately determining the composition and properties of geological formations, particularly in distinguishing between water, gas, and oil phases, especially in high salinity environments where traditional measurement techniques are inefficient and prone to errors.
Innovation Solution
A multi-detector pulsed-neutron tool system with long detectors and sigma measurements is used to characterize inelastic and capture gamma rays, enabling a triple phase evaluation by calculating gas saturation independently of salinity effects, and subsequently determining the volumes of water and oil using porosity and mass balance equations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional measurement techniques are used in high salinity environments, then the measurement process is simpler, but the measurement precision deteriorates due to salinity interference
Solution Approach 1:
The measurement process is segmented into multiple independent detection stages using different detector types (neutron detectors for porosity, gamma ray detectors for salinity, and additional detectors for fluid phase identification). Each detector measures specific parameters independently, allowing salinity effects to be characterized and separated from fluid phase signals, thereby improving measurement precision in high salinity environments without requiring a single complex measurement system
Solution Approach 2:
An intermediary measurement approach is employed where salinity is measured first using gamma ray detectors, and this salinity information serves as a corrective factor for subsequent fluid phase measurements. The salinity measurement acts as an intermediary step that enables accurate triple-phase evaluation by compensating for salinity interference in the neutron measurement signals
2Measurement precision
If traditional single-phase or two-phase evaluation methods are used, then the device complexity is lower, but the measurement precision deteriorates in formations containing gas, oil, and water
Solution Approach 1:
The evaluation method transitions from traditional two-phase (oil-water) to triple-phase (gas-oil-water) evaluation by adding a new dimension of measurement capability. This is achieved through combining porosity measurements from neutron detectors with fluid density information from gamma ray detectors and additional spectral measurements, creating a three-dimensional measurement space that enables differentiation of all three fluid phases simultaneously
Solution Approach 2:
The measurement system is designed with multi-functional detectors that perform multiple measurement tasks. The same detector array used for porosity measurement also provides fluid phase identification when combined with gamma ray measurements, eliminating the need for separate specialized equipment for each measurement type while achieving triple-phase evaluation capability
3Productivity
If traditional measurement and processing methods are used, then the processing time is longer, but the productivity is lower due to inefficiency
Solution Approach 1:
Salinity measurements are performed as a preliminary action before fluid phase evaluation. By measuring salinity first using gamma ray detectors and establishing baseline salinity characteristics, the subsequent triple-phase evaluation can proceed more efficiently with pre-characterized formation conditions, reducing the overall processing time while improving accuracy
Solution Approach 2:
The measurement system performs continuous simultaneous measurements of multiple parameters (porosity, salinity, fluid phase) rather than sequential measurements. Multiple detectors operate concurrently to collect all necessary data in a single measurement pass, eliminating the need for repeated measurements and significantly improving evaluation efficiency and productivity
Data Source
AI summary
Various embodiments include apparatus and methods to conduct a triple phase evaluation of a formation. The evaluation can be performed using a pulsed-neutron tool including a long detector and a detector to make sigma measurements. Additional apparatus, systems, and methods are disclosed.