New application for well test analysis: Locating closed perforation zones and damaged sections

• This paper introduces new application for well test analysis.
• Locating closed perforated zones and damaged sections in the formation is the new application for well test analysis.
• The impact of these two problems on pressure behaviors and flow regimes has been investigated.
• New flow regimes in the vicinity of the wellbore have been observed and analyzed in the research.

Closed perforations and damaged sections are two great challenges in the petroleum industry. Several reasons may cause these problems. Few of them depend on the type of formation and wellbore while others come from drilling, completion and stimulation activates before production process. Production rate and pressure drop may lead significantly to these two problems; therefore, production management sometimes plays a great role in controlling them. Millions of dollars are spent annually for the remedial process of these two problems. Therefore locating these closed or damaged sections is considered of great importance as an attempt to control them or reduce their negative impact on wellbore deliverability.This paper introduces a technique to locate the closed perforations and damaged sections using pressure transient analysis. Pressure behaviors and flow regimes in the vicinity of horizontal wellbores are affected by the existence of the closed perforated zones and the formation sections where the resistance to reservoir fluid flow toward the wellbore is maximized. This resistance occurs because of the damaged permeability and high skin factor. Analytical models for locating these sections and determining how many zones of the horizontal well that are considerably closed have been introduced in this study. These models have been derived based on the assumption that wellbore can be divided into multi-subsequent segments of producing and non-producing intervals. Producing intervals represent free flowing zones where there is no problem and both formation and wellbore are assumed to be clean. Non-producing intervals represent zones where both formation and wellbore's perforations are closed or damaged.The effective length of horizontal well where the perforated zones and the formation sections can not be considered problematic and the damaged length where both of them are significantly closed and damaged can be calculated. The numbers of the damaged zones can be calculated also. In addition, the locations of the damaged sections or closed perforated zones can be determined. Type-curve matching technique and the analytical models can be used for this purpose.