Abstract
Water hammer pressure has been known to cause formation fracture and well-control problems. Accurate prediction of water hammer pressure is crucially important to determine the selection of shut-in methods. In this study, the mathematic model of wellbore annulus transient water hammer has been established with the consideration of transient multi-phase flow characteristics, and it has been solved by the Method Of Characteristic (MOC). Finally, this paper focused on the effects of gas cutting, shut-in time and friction on water hammer pressure, and gas kick time were also regarded to study on the influence of water hammer pressure. The results show that both the gas cutting and gas kick time have few influences on the maximum water hammer pressure, but intensified the attenuation of water hammer pressure. Additionally, the peak value of water hammer pressure declines with the increase of the shut-in time, and the effect of friction loss on water hammer pressure became significant with the increase of well depth. More importantly, both the additional water hammer pressure and Shut-In Casing Pressure (SICP) generated by the closure of BlowOut Preventer (BOP) are likely to cause formation at the shallow casing shoe damage.
Highlights
Gas kick takes place from time to time during the drilling process when shut-in is required
The mathematic models were set up based on the following assumptions: 1. the fluid flow model in the wellbore is one-dimensional (1D) transient gas-liquid two-phase flow; 2. casing and drilling string are assumed to be linear elastic and the effects of cementing and formation are not taken into account; 3. the annulus fluid temperature profile is assumed equal to the formation temperature, and no heat transfer is accounted for; 4. drilling fluid and gas are regarded as compressible and the formation pressure is kept constant; 5. the influence of cuttings on water hammer wave speed is not considered; 6. the time for turning off the mud pump is not taken into account and the well control choke is closed before closing the annular BlowOut Preventer (BOP)
In order to study the variation of water hammer pressure resulting from the shutting-in of a kicking well, the distribution of flow parameters along well depth before shutting-in the well is needed to be determined by adopting multi-phase flow theory at first
Summary
Gas kick takes place from time to time during the drilling process when shut-in is required. He et al (2008) applied the method of Finite Element Method (FEM) to address the water hammer Partial Differential Equations (PDEs) and attempted to simulate water hammer by Automatic Dynamic Incremental Nonlinear Analysis (ADINA) finite element software This modeling method was formulated based on the assumption that the gas void fraction uniform distribution. Wang et al (2016) investigated the water hammer effect caused by the sudden intrusion of formation fluid into the drilling process, while it does not refer to shut-in and only limited parameters such as gas influx rates was analyzed The effects of related parameters, such as gas cutting, shut-in time, well depth and gas kick time, on water hammer pressure were investigated
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