Chemical Deliquification Multifunctional Product Development and Application in Low Pressure, Low Rate Gas Wells

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1 Clariant Oil Services Erik Welmer Dr Jonathan J Wylde Chemical Deliquification Multifunctional Product Development and Application in Low Pressure, Low Rate Gas Wells Erik Welmer and Dr Jonathan Wylde Clariant Oil Services

2 Presentation Outline Introduction Liquid loading of gas wells and impaired gas wells Mechanical methods for deliquification Foaming wells: solid foam sticks and liquid foamers Design criteria and experimentation for product selection Combined products CI and SI-foamers Field application and case histories Lessons learned and conclusions.

3 Gas Well Liquid Loading Very well covered in the literature as well as ASTM methods Put simply, liquid loading or liquid impairment is where liquid accumulated in a gas well lowers production A liquid loaded well is completely unable to produce A liquid impaired well has a faster than expected production decline due to hydrostatic loading Very common some studies estimate some 320,000 wells are impaired in NAm alone.

4 Deliquification Method Overview Many methods are available and are well summarized by Lea et al. (2003) No ubiquitous method exists as the optimum method is the most economic and lasts the longest Some techniques aim to increase the velocity of gas to lift water and reduce loading (e.g. gas lift, periodic production, velocity strings) Some aim to reduce the critical velocity, i.e. the point where fluid is unable to flow out of the well (e.g. compression, chemical addition) Alternatively mechanical methods also exist which include plunger lift, rods, ESPs, and swabbing operations.

5 Chemical vs. Mechanical Chemical deliquification offers an alternative (and often cheaper) to mechanical methods Mechanical methods are not always possible to install Mechanical and chemical methods can often be used in combination Each well is unique and requires a unique solution determined though.

Introduction Chemical Deliquification Two options for chemical deliquification (well enhancement) Solid foam generation sticks Liquid foam generation Introduction of chemicals can be

6 Introduction Chemical Deliquification Two options for chemical deliquification (well enhancement) Solid foam generation sticks Liquid foam generation Introduction of chemicals can be via: Batch treatment Continuous injection Selection of chemistry, dose rate and implementation is key Liquid soap is preferable more controlled and limits the likelihood of process upsets.

7 Generic Types of Chemistry Anionic: most popular, LES, AES, α-oes. Very polar and therefore water soluble although depending on salt type they can be rendered more oil soluble. Easy to winterize, can be incompatible with high TDS and HT Cationic: not common, quats (toxic), good however for high TDS, combination foamer/ci, and high condy Amphoteric: betaines and arguably the most ubiquitous chemistry to use, cat or anionic depending on ph, TDS and HT compatible, challenging to winterize Non-ionic: higher cost (e.g. ethoxylates of NPs, alcohols), cloud point issues at HT.

8 Field Application of Solid Sticks Automated launcher (pictured) Applied into the top of the wellhead during shut in Density of the stick ensures passage through the tubing to the bottom of the well and contact water Applications exist for drilling fluid foamers.

9 Solid Soap Stick Manufacture Also possible to blend sticks with: Acid Corrosion inhibitor Scale inhibitor. Alkyl Ether Sulfate (AES) / coco-betaine High Molecular Weight Polyethylene Glycol MW controls dissolution Nonylphenol Ethoxylate Moles of EO determines dissolution speed Mould to required shape Pour in liquid and cool Primary Foaming Component Heat flakes to MP of PEG Homogenize flakes Soap Stick long, diameter

10 Field Application of Liquid Soap Liquid foamer Pumped down annulus / through umbilical or capillary Defoamer can be injected to release gas Foamer is Injected to Increase bubble entrapment MICRO GAS DISPERSION (Foam)

Primary Foaming Component Corrosion inhibitor Scale

11 Liquid Soap Manufacture Possible to blend with: Acid Alkyl Ether Sulfate (AES) / coco-betaine Water / Solvent diluent Primary Foaming Component Corrosion inhibitor Scale inhibitor H 2 S Scavenger Etc. Secondary Function Component Liquid Soap

12 Design Criteria and Experimentation Many influencing factors that affect the choice possible foamer chemistry P&T, water chemistry, water cut and condensate contribute Factored into modeling routines output: generate a foam half life, defined as the optimum foam generation point The half life calculation is critical for optimum application in the field: Too low a dose rate and no enhancement will occur Too high a dose rate and process problems occur with foam carry over

13 Well Model Model inputs: Well geometry Well conditions Model outputs: Gas velocity and residence time Production data Half life of gas currently Estimated half life enhanced

14 Experimental Half-Life Determination 1,600 ppm 125 seconds 400 ppm 30 seconds 2,000 ppm 200 seconds 2,400 ppm 240 seconds. 800 ppm 70 seconds 1,200 ppm 120 seconds Sparge Method

15 Final Experimental Output Modeled Required Half Life

Combination Products The focus of this study was the development of

combinations of functionality including CI, SI, asphaltene and wax

given blend to a particular flow assurance challenge, e.g. the

16 Combination Products The focus of this study was the development of combined liquid products for use in Canada Many possible combinations of functionality including CI, SI, asphaltene and wax control, dyes, H 2 S scavengers and acid It is easier to tailor any given blend to a particular flow assurance challenge, e.g. the foamer / scale inhibitor ratio Two functionalities are of particular focus here: CI and SI.

Combination Product Design CI The challenge in Canada is that

CI and foamers can be deployed via batch or continuous CIs are often

amphoteric) foaming chemistries One example is a blend of phosphate

glycol matrix Continuous application can protect the production

17 Combination Product Design CI The challenge in Canada is that products nearly always need to be freeze protected to -40 C (-40 F) CI and foamers can be deployed via batch or continuous CIs are often cationic presenting blending challenges with anionic (or even amphoteric) foaming chemistries One example is a blend of phosphate ester, quaternary amine and betaine foamer in a methanol / water / glycol matrix Continuous application can protect the production tubing and further D/S whereas batch application usually protects the production tubing

the challenge One example of a formulated product is a blend of AES, phosphonate, methanol and water more

18 Combination Product Design SI The only effective option for combination foamer and scale inhibitors is to continuously inject Easier to blend as most SIs are anionic as are foaming chemistries MeOH compatibility is the challenge One example of a formulated product is a blend of AES, phosphonate, methanol and water more complex polymeric based products do exist Continuous application has the potential to protect the tubing and further downstream

19 Case History 1: 4 36 LP and low rate well produced bitumen leading to deposits 1 to 2 m 3 of produced water in the tubing would kill production Well was being treated with a liquid chemical foamer enhancement program (8 LPD of AES based product) A pump malfunction led to challenges maintaining production from the well and stagnant water gave a corrosion challenge A 20 L batch treatment CI/foamer strategy was developed and production was boosted from 0.9 e 3 m 3 /d (0.03 MMscf/d) to 4.5 e 3 m 3 /d (0.16 MMscf/d) After batching the well was reverted to the previous continuous injected product and prepump malfunction rates were realized as well as maintaining integrity

20 Case History 1: e 3 m 3 /d Batch CI/foamer 4.5 e 3 m 3 /d. 20

21 Case History 2: 16 4 The well was successfully treated with a batch treatment of high concentration, liquid chemical foamer and solvent Subsequent backside flushes and blowdowns kept the well producing, but eventually it would die off As a result of a RCFA, scale was identified as the flow assurance challenge The well was batch treated with an HCl treatment (one drum). It was then brought back online with continuous injection of 5 LPD of a combined deliquification foam generation and scale inhibitor product Production increased from the intermittent rates of 2 to 3 e 3 m 3 /d (0.07 to 0.11 MMscf/d) to initially 13.9 e 3 m 3 /d (0.49 MMscf/d) and a stable 10.1 e 3 m 3 /d (0.36 MMscf/d)

22 Case History 2: 16 4 Typical batch treatment 2.5 e 3 m 3 /d 6.0 e 3 m 3 /d.

23 Case History 2: 16 4 Acid soak and continuous treatment Acid Soak Continuous 13.9 e 3 m 3 /d SI/foamer initial 10.1 e 3 m 3 /d Stable.

24 Case History 3: 5 19 Very low pressure well (200 kpa) produced 5 e 3 m 3 /d (0.18 MMscf/d) Test work identified the chemistry required to enhance production and protect tubing that contacted stagnant PW Upon application of a 20-liter batch of combination foamer / CI down the well annulus, production increased to over 10e 3 m 3 /d (0.35MMscf/d) This increase remained for one week before slowly declining. Two weeks after treatment the benefit declined fully and re-treatment was required Chemical cost was insignificant compared to the additional 50 e 3 m 3 (1.76 MMscf) of gas produced over the course of a single treatment.

25 Case History 3: e 3 m 3 /d Batch foamer / CI 10.0 e 3 m 3 /d. 25

dose rate and optimization The case histories show that combination treatments can be applied to realize the added benefit

26 Lessons Learned and Conclusions Combination foamer and CI/SI treatments are possible that provide extra value over conventional deliquification Better results can be obtained using liquid products as it is easier to control the chemistry, dose rate and optimization The case histories show that combination treatments can be applied to realize the added benefit of solving more than one flow assurance challenge. Design and implementation however are key to success for these complex challenges.

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