Artificial Lift

Evolution of annular gas lift candidates and early results of application in the Delaware Basin. 

As horizontal wells deplete, there becomes a greater need to reduce bottom hole flowing pressure. Methods such as gas lift and jet pumping can be run into the curve but are limited in ability to drawdown bottom hole pressure. On the other hand, Rod pumps are most commonly used but, have difficulty running past a certain degree of wellbore deviation and suffer from gas locking and interference due to the slug flow.  A new gas anchor system has been developed to deploy into the horizontal section of the wellbore and has shown efficient in gas liquid separation.

The Dual Shot Acoustic Technique is used to troubleshoot Gas-lift Wells by looking for pressure communication between tubing and casing.  One gas gun is fired, sending a pressure wave down the tubing. Simultaneously, a second gas gun listens to the casing.  Both microphones are attached to the same input to record the acoustic signal.  The tubing microphone is disconnected immediately after creating the traveling pressure wave at the surface of the tubing, and the microphone on the casing detects signals that pass through defective valves or checks or holes in the tubing.

There are a large number of unconventional wells coming on line every month in the Permian Basin.  Most of these wells will have high bottom-hole pressures and initially flow on their own. However, after the initial flow back phase, pressures and rates decline and the well will begin to liquid load. At this point some type of artificial lift choice needs to be considered. This paper will lay out an artificial lift strategy for many of these wells that will transition from completion to depletion through various artificial lift options as a well’s production and pressures decline.

In today’s ever-more complex and corrosive downhole environment, especially in well sections with high dog leg severities, high water cuts and high sand content, it is challenging to develop a “one size fits all” coupling. Such coupling would need to be engineered to increase the life of the tubing and the coupling itself from basin to basin. Couplings may slap and then rub against the tubing, which consequently causes extremely aggressive angle contact to the tubing by the rod string, leading to coupling wear, coupling-to-tubing wear, and hole-in-tubing fail.

This paper will discuss the two API pump designations the rod pump and the tubing pump. The rod pump is occasionally referred to as an insert pump and has three variations; stationary barrel top anchor, stationary barrel bottom anchor, and traveling barrel bottom anchor. Available modifications that are not covered under API but are commonly used to improve run time or efficiency will be discussed. Several special design pumps will be described along with their advantages. A reader will be able to recognize the standard API pump designs, API designs with modifications, and specialty pumps.

Different types of forces NOT accounted for by the wave equation are 1) Mechanical Friction, 2) Piston Force on polished rod due to tubing back pressure and 3) True Vertical Rod Weight.  Mechanical friction due to 1) Over-tight Stuffing Box, 2) Down hole sticking due to Severe Dog Leg in wellbore profile and 3) Friction from Paraffin along a section of the rod strong.

Understanding wave dynamics can help improve rod design and operation. This presentation will illustrate the nuances of rod design and analysis through the use of visual representations of these abstract wave concepts. Dimensions such as time, rod loading, dynamic rod position, rod depth, dynamic rod stretch, rod velocity, etc. can be rendered against each other to create interactive plots in a three dimensional environment. These plots, while abstract in and of themselves, can provide intuitive clues as to the timing and location of key events during a pump cycle.

Tubing leaks have historically accounted for nearly half of the failures in the Hess Bakken wells. The root cause of these leaks is coupling on tubing wear; the non-metallic guides wear out, which results in spray metal couplings contacting the production tubing. To address this problem, the company installed ToughMet® 3 TS95 sucker rod couplings in over 650 wells, reducing the failure rate in the field. Data analytics was used to analyze the MTBF history over the last four years.
   

Gas lift is becoming a popular form of artificial lift in the Permian Basin for long horizontal wells that make high gas rates. Unfortunately the decline curves on most horizontal wells are not ideal. As the rates and pressure quickly drop gas lift starts to become inefficient and we are forced to make artificial lift changes in order to preserve base production. Rod pumps have always been the end of life application for artificial lift but it has been proven that pumping in horizontal wells can be very costly due to wellbore conditions.