Evaluation testing method for damage of drilling fluid to compact gas reservoir

Abstract

A disclosed evaluation testing method for damage of a drilling fluid to a compact gas reservoir comprises the following steps: drying a core sample, marking, performing uniform segmenting and slicing, and measuring the weight and other parameters of the dry core sample; putting the core segments into a fluid for infiltration and saturation; performing reverse centrifugation operation on the core segments, and acquiring the original water saturation Swi of the small core segment samples; measuring the nuclear magnetic resonance T2 spectrums of simulated stratum water and a filtrate of the drilling fluid and determining the difference; performing NMR imaging measurement on the fluid distribution state in the core; and putting the core segments into a core clamper of a drilling-fluid circulating instrument for measurement after the drilling fluid is circulated and calculating the water saturation Swi and the gas permeability K2 of the core segments, calculating the permeability damaging rate after infiltration of the drilling fluid by using the measurement results through comparison, so as to evaluate the damage degree caused by infiltration of the drilling fluid at different depths. The novel evaluation testing method for damage of a drilling fluid to compact and super compact gas reservoirs is established by improving an original slice method.

Description

technical field [0001] The invention relates to the field of oil and gas field development, in particular to an experimental method for evaluating drilling fluid damage during the drilling process of tight sandstone gas reservoirs. Background technique [0002] During positive differential pressure drilling, solid particles and liquid phases in the drilling fluid will inevitably invade the reservoir under the action of differential pressure, changing the original state of reservoir fluid distribution near the wellbore and possibly causing reservoir damage. Potential damage mainly includes four types: 1) Filtrate damage to the reservoir: under the action of the difference between the fluid column pressure in the well and the reservoir pressure, the filtrate enters the reservoir. The filtrate can cause the clay in the reservoir to hydrate and expand, or cause particles such as clay minerals in the reservoir to disperse and migrate to block the pores of the reservoir and cause ...

AI Technical Summary

Problems solved by technology

[0015] Using the core damage rate (DR) as the damage index method, the experiment uses the ratio of the permeability of the whole core before and after contamination to reflect the degree of damage to the reservoir by the drilling fluid, and there is no uniform standard for the length of the core

This method considers that the entire core has been damaged, so the evaluation cannot truly reflect the damage degree of the reservoir. In addition, the difference in the length of the core will have a great impact on the evaluation results; Thickness loss and damage, poor repeatability and reproducibility of the experiment, and strong heterogeneity of the core, it is difficult to control the process of measuring the permeability of the remaining rock samples to be constant; the resistivity method determines the invasion depth, and the measured resistivity and permeability The rate is the average value of the core section between the two measuring points. For the core with non-uniform intrusion, the value on the section is generally not equal to the measured average value.

The penetration depth and damage pollution degree obtained by the experiment are difficult to reflect the objective facts

[0016] In the method of determining the damage depth by using the core damage rate (SDR) of each section, the slice method needs to destroy the core, and the permeability of each section of the core before pollution can only be regarded as uniform, and the evaluation of the damage degree of each secti

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