Abstract
The main objective for the implementation of this methodology was to achieve uninterrupted production and avoid failures. Heavy oil wells undergoing CSS in the field in Kuwait, pose challenges of high temperature and sand incursion. As soon as the well was brought on production at the end of soaking period, Metal PCP, which was earlier believed to be the best choice proved wrong when it underwent failures due to dry run because of steam (gas) and the lost interference fit between the stator and rotor owing to reduced viscosity and poor efficiency due to fluid slippage. The strategy was revisited and Sucker rod pumps were initially installed as soon as the well came on production. Being shallow wells on VSD control, they were safely ran at 3 SPM and that kept the sand from entering the well since the velocity of the fluid kept way above the critical velocity. The pump produced around 100 bbl./day. As the reservoir cooled, and the viscosity increased, the calculated rod stresses were seen to increase beyond 80%. Anticipating the rod failures and the subsequent production loss, strategic decision to install all metal PCP was made for the next period of production. The increased viscosity of the fluid provided excellent efficiency to the PCP operation and also eliminated the rod fall. The well produced around 245bbls/day consistently. Thus the methodology states alternating the Sucker rod pump (SRP)and All Metal PCP (AMPCP) through the production cycle using viscosity as the indicator.
The cost and benefits of this approach was evaluated. The work over cost to replace the AL type against the costs due to failures and production loss was studied. It was concluded that this system provided the tangible cost benefit of around 30%, along with the uninterrupted production and conserving the heat energy in the reservoir. This method utilized the best combination of the performance features of SRP and PCP in their optimum operational brackets.
Considering the energy loses to the reservoir for a short period, which will be caused due to the work over rigs that utilize the cold mud fluids to replace the AL system or to clean the deposited sand which would cover the perforation, some design changes were made such as drilling the hole 1000 ft more than originally designed to maximize the production.
