CO2 Huff n Puff

20 December 2010 Hello everyone,

I am a new comer of this forum. I just found this is an exellent place where people can share knowledge and experience to each other.

I am working on an ad-hoc project namely CO2 Huff and Puff, in which we will inject about 100 tons liquid CO2 into reservoir section, then keep the well shut-in in 2-3 days for soaking CO2 before opening well for flow back. The purpose of this test is to determine how we can enhance oil recovery with CO2. At the time being, I have some concerns as followings and appreciate if you could share your experience on these.

1) The CO2 will be injected into wellhead at ca. 2,000psia and 5degF (-15degC). Depending on CO2 pumping rate, the downhole equipment will be cooled down consequently. There are several concerns with this extremely low injection temperature such as brittle cracking to the tubing or completion assembly (packer, PBR, TRSV, etc). Therefore, I am thinking about increasing CO2 temperature by heating up prior to injecting into well but the contractor here they do not have any experience on that. Can you share your thoughts?

2) Current plan is to use 4-1/2” 15.5# T-95 tubing (rental) as work string. Even the flow back period (after injection CO2 & soaking) is only maximum 4 days, but there is still a concern with CO2 corrosion to T-95 grade. I am doing some research with corrosion book to determine the level of carrion in such short period of time but it is really valuable if I can have field track record from other location where CO2 project was performed.

Some info. during well flowing back (max. 4 days) is as follows.

o Downhole temperature: est. 100degC

o Downhole pressure: 2,500 to 3,000psi

o CO2 gas percentage: max 95% in first few hours of well openning

o Cl-: ca. 20,000ppm of formation water

o Water rate: ca. 50 bpd

o Liquid rate: 300 blpd (oil + water)

o Gas rate: max. 3,500 Mscfd in first few hours after opening well, and then reduce quickly to about 200Mscfd.

Thank you in advance.

Best regards,
Huy

(Vu Huu Huy)
Petroleum Engineer
Japan Vietnam Petroleum Co

1 Answer(s)

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