| Popis: |
Reservoir pressure depletion and liquid loading depress production in mid-to late-life producing wells. While pressure depletion can be difficult to combat and requires large scale solutions, liquid-loaded production tubing is easily remedied by on-site, individualized artificial lift solutions, such as sucker rod pumping, plunger lift, or gas lift, to name a few. A recent experimental study of Coutinho et al. (2017), using 2,788 ft depth vertical well with 2.88-inch ID tubing and 4.89-inch ID casing, shows that liquid-assisted gas lift (LAGL) processes can overcome difficulties in conventional gas lift, one of the most popular artificial lift methods in both onshore and offshore environments, and aid in cost reduction for operations by decreasing the onsite energy and infrastructure needs to unload a well.Following the outcome of the experimental study, this study investigates how to further refine LAGL operations by conducting transient computer simulations using OLGA. The first step is to match the experimental data (i.e., history of bottomhole pressure and injection pressure) to extract model parameters for the simulations to follow, the second step is to perform 119 different simulation runs as well as analysis of resulting pressure and liquid-holdup histories in a wide range of gas and liquid flowrates, and the last step is to show how to implement the optimization technique by using the contour maps of variables and parameters of interest to optimize.The results show that the two contour maps of required maximum injection pressure and liquid holdup in the tubing, as a function of gas and liquid flowrates, can serve as a useful means of seeking the optimum operating conditions. In addition, it is also shown that there are multiple sets of two contour maps, equivalently, to be employed for a similar analysis depending on various field scenarios or constraints (such as compressor capacity, limited gas supply, and separator capacity). Pressure loss and phase fraction, through complicated multiphase flow physics and flow regimes, play a key role behind the presence of optimum operating conditions during liquid unloading process. |
