Abstract
Aiming at the problem that the existing risk assessment methods in China cannot simply and accurately assess the safety risk of gas wells, a rapid semi-quantitative risk assessment method for gas wells under high temperature and pressure is studied. Based on the rapid risk assessment method of annulus well with pressure in Chevron Company and the existing risk assessment methods, the well barrier and annulus pressure of high temperature and high pressure gas wells are fully considered. A rapid semi-quantitative risk assessment method for high temperature and high pressure gas wells is established, which takes the annulus pressure value, well service life, annulus pressure recovery after pressure relief, reservoir conditions (formation pressure, production) and well CO2 and H2S content as the key risk indexes. The method is applied in a gas field, and the risk value and risk grade of a practical well are semi-quantitatively evaluated. The overall risk situation of the well is obtained. The research results provide important technical guidance for the safe production of gas well.
Highlights
Aiming at the problem that the existing risk assessment methods in China cannot and accurately assess the safety risk of gas wells, a rapid semi-quantitative risk assessment method for gas wells under high temperature and pressure is studied
From 2006 to 2008, foreign scholars established wellbore integrity management system under different formation conditions by risk matrix method [4] [5]; Seyed-Hosseini S M and others developed wellbore integrity management software, created wellbore integrity management methods and measures [6]; In 2009, Sultan A et al proposed the method of quality identification and safety check of wellbore and its components in each stage of oil and gas wells [7]; in the same year, Freij-Ayoub R, et al created axisymmetric numerical model combined with FLAC3D to study the risk assessment of casing in natural gas hydrate [8], in 2012; J
Based on the above situation, a set of rapid semi-quantitative risk assessment methods for gas wells is proposed by combining the existing risk assessment methods with the rapid risk assessment method of annulus well killing in Chevron Company, taking into account the scientificity and operability
Summary
China’s gas resources are very rich, is an important source of China’s oil and gas resources supply, since 2019, China’s natural gas upstream industry investment has increased significantly, with a series of exploration found, to achieve a substantial increase in reserves and production, gas development encountered wellbore integrity problems are increasingly serious. In 2002, A.S. Abou-Sayed et al analyzed the geomechanical model to evaluate the factors affecting the stability of casing [1]; in 2004, Jamal Al-Ashhab et al established the wellbore integrity management system through the risk matrix method, and evaluated the integrity of the whole life cycle of gas wells [2]. The above scholars have proposed or developed risk assessment methods, but they all focus on quantitative or qualitative methods, and the application process is complicated, which often cannot meet the requirements of batch high accuracy analysis of risk factors of domestic gas wells. For wells that cannot be judged as low risk by preliminary classification of well integrity risk level, rapid semi-quantitative risk assessment is carried out considering the main risk factors of gas well annulus pressure. According to the integrity of the well barrier to conduct a preliminary screening analysis, the basic overview of the well barrier status
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