Abstract
The analysis of string stability affected by earthquake in the shallow of deepwater drilling
In deepwater drilling, wellhead, catheter, surface casing system and riser are linked together, they show the characteristic of instability under the influence of wave force. Some scholars have already done some research on this topic, however, the shallow sea is an area with frequent earthquake. Especially in some active seismic zone, oil and gas are often accompanied by earthquake, so it is crucially important to study the seismic forces on deep-water shallow wellhead, catheter and surface casing.
On account of the dynamic pile soil, the paper firstly studies the classification of the shallow soil properties. The paper carries on an overall study as landing depth of surface casing is about establishes the neural network model, considering the length, diameter, vertical pressure, casing pipe weight, soil properties, pore pressure, shallow properties of drilling fluid and especially the seismic characters of surface casing string. The influence of earthquake on the casing string stability will be gotten from these data collected after neural network analysis and calculation.
Based on the geological characteristics of Yingqiong basin, this paper establishes the neural network input and output bridge, obtains the earthquake effect on shallow casing string, and get the following conclusions: 1. Natural environment and other factors have certain effects on the casing string stability; 2. Traverse force on casing string increases by the earthquake action; 3. The earthquake has greater influence on the wellhead stability; 4. Shallow casing string vibration frequency can be obtained during earthquake action.
Study of Vibration of casing string in deep-water has been the difficulty of research. As many accidents happened due to multiple factors, shortages in current study, it is particularly important to research on how to build a deep shallow casing string vibration model, especially considering the uncertainty of seismic force. Importance of this paper is the further study of the influence of the seismic force.
