# Research Status and Development Direction of Formation Damage Prediction and Diagnosis Technologies
## 1 Introduction  
Formation damage has been a significant topic for decades. The Society of Petroleum Engineers (SPE) has been holding academic conferences on formation damage every two years since 1974. Formation damage occurs during drilling, completion, workovers, production enhancement, and extraction operations when the physical, chemical, or biological equilibria of formation rocks, minerals, and fluids is disrupted [1, 2, 3]. This leads to reduced production efficiency [4, 5], increased operational costs [6, 7], and, in severe cases, well abandonment in low-permeability formations [8, 9]. Table 1 summarizes common types of formation damage and the corresponding causes. In general, the types and properties of oil and gas formations are complex and dynamic, and they can have elevated temperatures, high pressures, and pore-slit holes coexisting in the same formation. Additionally, a formation seepage space has multi-scale structural characteristics. Moreover, there are many operational steps and long damage times, and damage mechanisms and protection measures vary greatly between different regions and distinct types of formations [10, 11, 12]. Formation protection should be prevention-oriented, combining prevention and treatment. Therefore, it is important to predict possible damage and accurately diagnose it if it occurs in order to prevent and relieve formation damage effectively.  
Efforts to address formation damage have led to the development of various prediction and diagnostic techniques, including wellsite diagnostics, laboratory experiments, numerical modeling, and artificial intelligence [13]. Laboratory tests and numerical methods include laboratory experiments, analytical modeling, numerical simulation, and artificial intelligence methods. These predictive and diagnostic techniques can help develop suitable measures to prevent or undo formation damage, characterize the severity of formation damage (qualitatively or quantitatively) in order to reduce or avoid formation damage, and efficiently relieve damage at minimal costs while avoiding costly production enhancement operations [14; 15].  
As research advances, various methods for predicting and diagnosing formation damage are being developed, each with its own advantages in terms of science and economy. The emergence of advanced experimental equipment and observational tools (NMR technology, tracer technology, X-ray scanning, mass spectrometry, scattering neutron sources, and others) have made it possible to study the damage mechanisms of different formations from a pore scale (or a small-scale) to mesoscopic and microscopic scales with great advantages, offering 3D imaging of internal structure of the core samples at high resolutions. For some time, despite a great number of research studies on this topic, formation damage prediction and diagnostic techniques have still lacked systematic theoretic explanations and accurate measurements. Therefore, in order to improve the theories and technologies of formation damage prediction and diagnosis, it is crucial to highlight the current progress and gaps in the literature. Therefore, this study sheds light on different published research studies on formation damage diagnosis and prediction technologies, analyzes the problems and challenges of existing formation damage prediction and diagnosis technologies, and indicates their future development direction.