Research and application of high-resolution micro-cylindrically focused logging tool

Abstract

The unknown nature and complexity of non-uniform formations cause new difficulties and challenges to the accurate detection of electrical instruments in shallow formations. The micro-cylindrically focused logging tool (MCFL) can provide three original measurement curves, RB0, RB1, and RB2, with different detection depths, which reflect the flushing zone resistivity, mudcake resistivity, and mudcake thickness. In this study, the finite element method was used to model and analyze the micro-cylindrically focused logging tool tool in a three-dimensional non-uniform medium model. By converting the partial differential equation into a generalized polar problem, the logging response characteristics of the micro-cylindrically focused logging tool tool at different detection depths and ranges, mudcake thicknesses, flush zones, and mudcake resistivity contrasts were investigated. Inverse processing of the micro-cylindrically focused logging tool data using the least-squares method was used to obtain the flush zone resistivity, mudcake resistivity, and mudcake thickness, based on which the micropotential and microgradient curves were synthesized. In addition, a digital focusing method was proposed to improve the focusing accuracy and flexibility of the instrument, enhancing the performance of the micro-cylindrically focused logging tool. The optimized design of the focusing method significantly improved the detection performance of the pole plate. This plays an important role in the evaluation of thin layers and oil-water reservoirs.

A standard calibration method based on a symmetric resistance network matrix for galvanic logging instruments

“…Subsequently, various lateral logging technologies have been developed, with an improvement in the measurement accuracy by focusing on electrodes. Currently, the most commonly used tools in China are the HRLA (Schlumberger Company), HDLL array lateral (Atlas Company), and microcolumn focused logging tools [ 1 – 3 ]. Schlumberger’s HRLA instrument has 16 electrodes that can adequately describe the anisotropy of the formation [ 4 ].…”

“…Gerami [ 10 ] used Kirchhoff’s current and voltage laws to calculate the potentials of all nodes in the wireframe model of an equivalent resistance network. Taking microcolumn-focused logging (MCFL) as an example, 9 electrodes require 36 resistors to simulate complex formations, whereas HRLA requires 120, therefore necessitating the development of a calculation method for realizing large resistance networks [ 3 ].…”

“…The latest MCFL adopts the digital focusing method, which avoids the problem where equipotential hardware focusing cannot eliminate the residual voltage; it has been widely used in major oil fields in China. Fig 1 shows the electrode distribution and working principle of the MCFL [ 3 ].…”

“…Here, R xo can be inversed using Eq ( 2 ) [ 3 ]. The calibration coefficient, k i is typically measured using a sophisticated circuit.…”