Chemical Foamers for Gas Well Deliquification
the resultant benefits. A jump in production was recorded and a positive impact on the decline curve was observed.5
In some wells batch treatment is the more appropriate option. This offshore condensate-loaded (>90%) well was on cyclic production, shutting in every six to eight days. Using the novel condensate-tolerant foamer, a single batch treatment was performed, dosing ~30,000ppm foamer into the well’s liquid column. After a 24-hour shut-in the well was flowed back with outstanding results compared to flowback when no chemical was present. Table 1 shows that within the first 30 minutes the gas rate increased and a significantly greater volume of condensate came to surface. With continued monitoring the volume of condensate recovered exceeded the volume that was reported to be in the well, demonstrating a complete well unload. This was confirmed by the huge increase in flowing time – almost 10-fold – before the well was shut in again. In addition to these production improvements there was no impact on basic sediment and water or oil-in-water levels.6 considering the foamers thus far it has been as an isolated treatment.
When
An advantage of these chemicals is that they can be successfully employed to support and enhance mechanical lift methods. Applying the chemical to plunger systems and velocity strings are two scenarios where the gains have been significant, increasing flowing time.
An Encouraging Future
The application success of foamer chemicals indicates an encouraging future for such technology. To enhance product offerings further there are a number of focused research areas:
• Hydrocarbon foamers to enable treatment of all mixed systems, even at very low water cuts.
• Combination products – foamers that include corrosion inhibitors, scale inhibitors, desalting agents and/or paraffin inhibitors. This is of benefit as less chemical is required onsite, treatment programmes become less complex and single, potentially already installed injection lines can be used to manage multiple issues.
• Environmentally sustainable product line is the goal, working to regulatory requirements to offer ‘green’ products.
• Gas-lift products for application in systems that require more lift capability or need to reduce the gas volume injected. Due to the conditions of gas injection, special formulations are required.
• Squeeze treatments: applying foamer as part of a scale squeeze or independently. This is designed to enter the formation so it requires products that are demonstrated to have no impact on the rock.
Conclusion
In summary, liquid loading plays a part in every gas well’s life-cycle. The liquid build-up within the casing and tubing severely affects production to the point where the hydrostatic pressure will kill the well. Artificial lift – mechanical or chemical – is acknowledged as a requirement to address this issue. Mechanical solutions are well established, but due to a number of operating considerations may not
1. Lea J, Nickens H, Wells M, Gas Well Deliquification, Gulf Professional Publishing, Massachusetts, 2008.
2. Nguyen D, A Statistical Design Approach: High Condensate Foamers, presented at the European Gas Well Deliquification Conference, 2007.
Figure 3: Foamer Treatment Above Critical Tubing Velocity
1,000 1,200 1,400 1,600
400 600 800
200 0 Date Production Pre-foamer trend Well critical velocity
Table 1: Production Results from Foamer Treatment in an Offshore Condensate-loaded Well
North Sea Field Trial – DH Batch Variable
Previous Flow-back
Condensate within 30 mins (bbls) 5 Gas rate after 30 mins (mmscfd)
40 5
Condensate after 12 hours (bbls) 50 Well uptime (days)
6–8
6.5 81 63
700 30 62
>685
always be preferred. The science of surfactant chemistry has developed a new generation of foamers that are versatile alternatives. Available foamer technology has been developed to address numerous application challenges. The products have undergone a rigorous development process, from fundamental laboratory testing to performance evaluation and field trials. The results of field trials support the conclusions made in the laboratory and validate the modelling used to identify candidate wells.
Treatment in the field can be by batch or continuous. Batching is often advised for a well that has been shut in or for an initial trial, but the preference is for continuous application. This has shown improved rates, controlled decline curve and consistent production. Optimisation of the treatment is easy due to the short period between treatment and response, enabling operators to achieve maximum value. In addition, the chemicals can be combined with established mechanical lift methods to offer further benefits. Research efforts continue to improve and broaden the efficacy and applicability of foamers to provide more options when it comes to production management.
Chemical foamers are a proven option for tackling liquid loading in gas wells and can reward the operator in many ways. It is with technology such as this that more gas can be produced and the sustainability of the gas industry enhanced. n
3. Coleman SB, Clay HB, McCurdy DG, J Pet Technol, 1991;43:329–33.
4. Turner RG, Hubbard MG, Dukler AE, J Pet Technol, 1969;1475–82.
5. Willis MJ, Hudsen J, Dean C, Foamer Field Trials in North
Louisiana, presented at the European Gas Well Deliquification Conference, 2007.
6. Visser J, Willis M, Selection and Application of Chemical Foamers for Offshore, North Sea, presented at the Gas Well Deliquification Conference, Denver, US, 2009.
Trial Results % Gain
Added foamer
EXPLORATION & PRODUCTION – VOLUME 8 ISSUE 1
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Production rate/MSCF
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