Abstract

With extremely challenging and unforgiving ultradeepwater environments combined with those of high-pressure, high-temperature (HP/HT) reservoirs, the costs associated with not understanding each unique dynamic environment could be very high. The complexities of the hardware systems are akin to human beings' internal systems, involving dependent and independent interactions. When these complex systems are deployed into unforgiving environments without appropriate safeguards/assurances, unforeseen adverse issues will eventually occur.

To help reduce the likelihood of calamitous failures or well completion issues, prejob perforating and well construction simulations have become industry standard. Notwithstanding the utilization of industry accepted models, issues continue to arise. Assurance models that were previously industry-standard lack the complexity of newer, improved systems on the horizon that are better able to quantify the dynamic events experienced in these extremely challenging environments. In essence the modeling technology has not kept pace with the present environments we perforate in.

Understanding and managing stress and shock loads imparted to downhole tools during their full range of operating conditions is critical to the reliability of such tools. In the case of a perforating gun string, the energetic material detonation forces inducesignificant stresses on adjoining tools (Dobratz 1985). This paper discusses the case of a perforating string affecting an adjoining interval control valve (ICV) in the tubing string by a 4 5/8-in. gun system.

One of the most significant stresses experienced by downhole equipment is the loading imparted by the release of energetic material detonation forces during downhole perforating. Knowledge of the dynamic response of downhole perforating gun strings during detonation is critical to the development of better performing gun systems, equipment, and optimal job designs with maximum reliability.

Numerical simulation is central to advancing this understanding, but available simulation tools have generally been limited to hydrodynamics models focused on optimizing shaped charge perforating performance (Han et al. 2010) and to highly simplified string and wellbore models lacking the fidelity required to capture the full system behavior with sufficient accuracy. Limited value of current models has been attributed to the general lack of relevant data needed for proper model calibration and validation.

Approaching the development of a resolute system model that addresses these shortcomings required not only an appropriate treatment of physics throughout the simulation time frame of interest but also the collection of relevant and reliable data with which to calibrate and validate the system model.

A two-pronged software and hardware approach (Craddock et al. 2014) was developed to obtain an accurate picture of the dynamic shock response of the bottomhole assembly (BHA) and wellbore fluids during a detonation event. The finite-element-based simulation software package bridged the gap between existing software tools. It was used in tandem with a new downhole sensing sub that supported the simulation effort by capturing the necessary data to calibrate and validate the software. Key attributes of the sensing sub are it can be run with the detonation event and can measure gun string loads in addition to pressure, acceleration, and temperature. Downhole data collected from multiple field trials was used to evaluate the performance of the sensor sub and simulation software. New surface testing tools and methods were also implemented to support initial model calibration and to verify certain critical aspects of the downhole sensing sub design. The effort has successfully demonstrated the ability to collect high-quality data from within the perforation zone and the ability to accurately simulate string and wellbore dynamics. These are both indispensable capabilities which enable the detailed study of the 3D dynamic response (Glenn et al. 2014) of the ICV in the tubing string by a 4 5/8-in. perforating shaped charge detonating gun system.

The general purpose multiphysics simulation software capable of simulating a wide range of physical events, including structures coupled to fluids, is of interest and is discussed. The principal advantage for results validation is the model will run inside the same environment, and has explicit and implicit solvers. The 3D shock loading finite-elemental analysis (3D SL FEA) contains approximately 100 constitutive models and 10 equations-of-state for material behavior. This is enhanced with the addition of the bolt-on module that can quickly build visualizations to analyze the data using qualitative and quantitative techniques. The data exploration can be done interactively in 3D or programmatically using batch processing capabilities.

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