# Modeling of Swab and Surge Pressures: A Survey
## 2 Literature Review of Five Prominent Works on Swab and Surge Models
### Surge and Swab Modeling for Dynamic Pressures and Safe Trip Velocities
#### 2.1.2 Analysis of the Work by [PERSON]  
The main feature of the work [4] is the computer program to predict the maximum swab and surge pressures, the variations of swab and surge in the time domain at the bottom wellbore, and casing when running a casing, liner, or drill pipe stand. The computer program also generates warnings of lost circulation for surge or influx for the swab.  
This work presents the main features of the theory for the model and a computer program. Based on the theoretical development of the dynamic swab and surge model, the computer program has been written, tested, and validated to some extent based on limited measured data. It simulates conditions in boreholes with fairly complex geometries, considering casing, liner, open hole, tricone or diamond bits, and the return area around the bit, drill collars, special pipe, or top drill collars, and drill pipe. The computer program has the following main features:  
1. It predicts the maximum surge or swab pressure or their variation with time at the bottomhole and casing-shoe when running a casing joint, liner, or a drill pipe stand;
2. It warns about the danger of lost circulation for the surge (or kick for the swab) when the computed maximum pressure (or minimum pressure for swab) exceeds (or falls below) the specified pressure margin or the maximum (or minimum for swab) equivalent mud weight. For each case, it computes the maximum safe trip speed in order to avoid the lost circulation or the kick problem. These answers can be obtained while running in or pulling out the pipe at various distances from the bottom of the hole.  
Based on the computer program runs, the authors had the following conclusions regarding swab and surge pressures:  
1. The computations of swab and surge pressures based on steady-state flow are generally incorrect given the unsteady nature of the flow;
2. As far as the effect of various parameters on the swab and surge pressures is concerned, these parameters can be listed, in order of their importance, as follows.  
The most critical parameters are the maximum trip speed and various parameters in hole geometry, such as the size of the hole and various pipes, and the depth of the well and the relative depth at which a pipe is being run. From the given example, one may run a pipe at a higher trip speed when running at large distances from the bottom, but one must carefully note the increase in surge pressure at the casing shoe when the pipe is close to it. The effect of the expansion of the hole and other conduits is also significant. In the case of the drill string, the plugging of the jet nozzles in tricone bits (or crowfoot area in diamond bits) and the constriction of the annulus return area can also significantly affect the swab and surge pressures. Regarding the effect of mud parameters, the increase in yield value has a maximum. However, not as many preceding parameters affect the surge pressure, followed by the plastic viscosity and mud weight. The mud weight appears to have a relatively small effect on the surge pressures.  
The computer program written for the model includes almost all the significant parameters. It is user-friendly and has fast run times. It accurately predicts not only the maximum surge pressure or its time-variation at any point in the well but also computes the safe maximum trip speed when running a casing, liner, or drill string at a given depth in the borehole.