Overview of Leak-Off Test and Formation Integrity Test: Test Interpretation and Pitfalls

Formation strength tests, such as formation integrity test (FIT), leak-off test (LOT), and extended leak-off test (XLOT), are crucial for maintaining wellbore stability. Wellbore stability issues are the main reason for nonproductive time (NPT) especially in the drilling operation. Therefore, it is important to understand the stresses around the wellbore to better interpret the formation strength tests. These tests are carried out to (i) test the casing shoe strength, (ii) estimate the minimum horizontal stress, (iii) derive the maximum horizontal stress, and (iv) estimate the fracture pressure gradient. By understanding the stresses around the wellbore and the results of the formation strength tests, engineers can make informed decisions about casing design, cementing practices, and drilling operations. This can help to prevent wellbore instability and NPT, which can save time and money. This study comprehensively reviewed, examined, and analyzed all the available tests currently employed in the field. The goal is to provide an in-depth understanding of each technique and to identify any potential limitations. A deep literature review was conducted to identify all the available tests. Each test was examined in detail to understand its purpose, methodology, and limitations. Then, the results of the tests were analyzed to identify any trends or patterns. The findings of the study were summarized and presented in this paper. Several factors were considered in the analysis of the tests such as formation permeability, formation strength, stresses around the wellbore, fluid properties, and mud type. The results of the study can be used to improve the understanding of formation strength tests and to develop more accurate and reliable methods for interpreting the results. The study considers several factors in the analysis of the tests, such as formation permeability, formation strength, stresses around the wellbore, fluid properties, and mud type. This is different from previous studies, which have often focused on a single factor or a small number of factors.