GALLOP System a Novel Artificial Lift System to Deliquify Horizontal Gas Well
D. Croce1, R. Brito1, S. Wilson2
1: Colorado School of Mines
2: Wilsonsmls Enterprises, LP
In order to produce from horizontal wells, drillers tend to “surf” up and down to follow permeability steaks or optimize complex well trajectories. This design creases predictable, but unfavorable fluid distributions in the wellbore and adversely affectsflow characteristics. A proven unavoidable problem is an increase erratic production caused bytrapped-gas induced slugging, liquid loading, film reversal, water accumulation, terrain induced slugging, and pre-mature well abandonment.
These conditions lead to reductions in well production, intermittent flow, no-flow, equipment mechanical fatigue and failure, and acceleratedpipe corrosion. At a reservoir scale, there is a reduction of the formation conductivity due to relative permeability blocking, sand plugging, scale deposition, shale swelling, and sand production due to cyclical loading. So far, the solution to minimize liquid accumulated in horizontal wells has been to use artificial lift (AL) methods designed 30-50 years ago for vertical oil wells.
More recently, experimental and field observations have indicated that these methodsare not as effective as had been hopedin horizontal wells, yet the problems are often hidden to operators who may not realize the potential up-side of more effective liquid removal. Traditional AL systems have a poor performance record and fail sooner than expected, increasing operational expenditures and reducing hydrocarbon recovery. There is an urgent need to develop new technologies to produce, monitor, troubleshoot, and optimize the production onthe growing inventory of mature horizontal wells.
This study presents preliminary experimental and transient modeling results for a novel artificial lift system named Gas Assisted Liquid Lift OscillatingPressure(GALLOP). The method is designed to use a closed-loop intermittent gas lift system to lift fluids from specific locations along the horizontal wellbore.
The GALLOP system is composed of a dual small ID U-tube run along the entire wellwith check valvesstrategically located along the liquid filled sections of the horizontal wellbore. When de-pressurized, the U-Tube fills with liquid that has flowed into the production casing. Once full, the U-Tube can be evacuated to the surface by applying gas pressure to one end at the surface, producing the other end to a tank. The small IDs reduce the required amount of gas to inject and increase the gas velocity and volume of removed liquids. In contrast to the very popular plunger lift systems, GALLOPuses pressure pulses that are only experienced by the GALLOP piping, allowing the well/reservoir to be produced continuously. This allows the steady buildup of liquids and reduces the amount of injected gas and surface facilities required.
The objective of this study is:
1)to determine the potential of using this method to deliquifyhorizontal wells,
2)to optimize the system performance by maximizing the liquid removal, and
3)to minimize gas injection volumes and required wellhead injection pressure.