Liquid Loading Mitigation: The Right Method For The Right Well At The Right Time
Ewout Biezen, Stathis Kitsios, Rob Smeenk
Nederlandse Aardolie Maatschappij (NAM)
Shell in The Netherlands
Abstract
Liquid loading (LL) currently affects a capacity of approximately 3.5 MMm3/d in the NAM onshore Netherlands area.
Properly managing tail-end production requires a proactive approach to mitigating liquid loading in order to avoid deferment and loss of ultimate recovery. A well in its tail-end production phase may receive multiple liquid loading solutions over its lifetime.
A number of LL mitigation methods can be used to improve the tail-end production of liquid loaded gas wells. In this paper we will present the methodology we use to select the right method for the right well at the right time. Ultimately it is the goal to optimize and extend the tail-end production of our mature gas fields using a lifecycle approach.
The first important step is the proper understanding of the well in- and outflow behavior through modeling of all wells, not just the ones that are just becoming liquid loaded. A complicating factor is the variety of completion sizes and designs that may be prohibitive to apply certain solutions. In our efforts we make use of a number of diagnostic methods to identify and predict liquid loading in wells (acoustic logging, static and flowing gradients, WGR measurements, historical well performance). This helps in predicting the onset of liquid loading in wells and in preparing for the solution in good time. On the basis of pre-defined criteria we can then determine which solutions will clearly NOT work and shortlist the options that do have potential. This approach allows us to plan upfront for implementing the most promising (sequence of) solutions (e.g. velocity string, continuous foam, tailpipe extension, wellhead compression, plunger lift).
As planning for the tail-end production solutions takes time, the practical approach is to start using batch foamers as soon as liquid loading signs become evident in the production behavior. This is tested in a rigorous manner to obtain reproducible results and determine if foaming is a viable solution for the wells under consideration. Of course if water and condensate samples are available pre-screening lab tests can be done to select the most promising foamers rather than resorting to trial and error.
The paper will present the criteria that are used to screen candidates, the results we are currently seeing from this pro-active approach, and the plans for the near future.