Combining experimental and logging data for calculation of the true skin factor of a horizontal well

Abstract

Abstract Horizontal wells are an effective way to develop oil and gas fields with large drain areas, leading to high production rates and recoveries. They have been widely used in low permeability oil‐gas reservoirs, shale gas reservoirs, coalbed methane reservoirs, and so on. To achieve the best production rate of horizontal wells, it is essential to further reduce drilling completion fluid damage to protect the reservoir. The skin factor is the main indicator for evaluating the degree of damage of the drilling completion fluid on the reservoir. However, the skin factor obtained by field tests is the sum of the pseudo‐skin factor and the true skin factor, which cannot precisely evaluate the degree of damage. Therefore, it is important to calculate the true skin factor to correctly evaluate the degree of damage of the drilling completion fluid on a reservoir during the drilling completion process of horizontal wells. In this work, a combined method based on experimental data and logging data is proposed to calculate the true skin factor. First, based on a drilling completion fluid dynamic damage experiment, a relational expression between the initial permeability and the damaged permeability is equated, and then, a relational expression between the permeability of rock samples and the filtration velocity of the drilling completion fluid is formulated. Second, after combining experimental results with logging data, the horizontal reservoir intervals are subdivided and both the damaged permeability of the partial reservoir intervals and the major semiaxis of the damaged ellipse are calculated. Finally, the true skin factor of the horizontal well is computed. This metric provides a more precise evaluation of the effect of drilling completion fluid on a reservoir.

Keywords

• logging
• orizontal wells
• reservoir damage evaluation
• reservoir protection
• true skin factor