South Timberlier Area, Gulf of Mexico

The subject well had experienced a Sustained Casing Pressure (SCP) problem for several years in the
13-3/8″ x 9-5/8″ annulus. Diagnostics indicated that the pressure source was most likely a zone at the 13-3/8″ casing shoe, traveling to the surface via a microannular channel. When bled to zero, the pressure would increase to 1015 psi within 3 hours. A sustained flow of approximately 1.6 gallons per hour was recorded.

Seal-Tite® International injected approximately 30 gallons of customized sealant, filling the microannulus to an estimated depth of over 4000 ft. Once the sealant was allowed to cure, the annulus was bled off and the pressure
response recorded. The pressure held at 0 psi for several days, and then began building at approximately 60 psi per day until the original pressure of 1300 psi was reached.

A second sealant treatment of 25 gallons was then pumped into the microannulus and displaced with nitrogen.
After one week the nitrogen pressure was bled off and the annulus pressure observed. After a period of 43 days, the annulus pressure has fluctuated between 75 psi and 300 psi, apparently in relation to thermal effects.

Background:

The subject well was completed in November, 1991 with a TD of 14,310′ MD. The casing program consisted of 30″ drive pipe, 20″ surface, 13-3/8″ & 9-5/8″ intermediate, and 7 ” production. The casing string characteristics are listed below:

Casing String Shoe Depth Burst Collapse Cement Info
30” 254 ft Drive Pipe
20” 1,010 ft Details unknown – reported to surface
13 3/8″, 68#/ft N80 Butt 4,499 ft 5,020 psi 1,950 psi Details unknown – reported to surface
9 5/8″, 47 #/ft S95 Butt 11,371 ft 8,150 psi 5,080 psi Details unknown – reported to surface
7″ 32#/ft P-110 LT&C 14,200 ft 11,640 psi 10,760 psi Details unknown – reported to surface

In August, 2002 the Operator contacted Seal-Tite® International to evaluate and possibly repair the subject leak Seal-Tite® specializes in repairing leaks in various systems for the oil and gas industry. Recently they collaborated with Cementing Solutions Inc., a recognized industry expert in oilfield cement systems, to develop sealants and methodologies specifically for microannular problems.

Leak Analysis:

On site diagnostics conducted by Seal-Tite® technicians indicated a stabilized fluid feed-in rate of 100 ml/min, and the ability to pump into the microannulus at 2 liters/hour at 1200 psi, increasing to 17 liters/hour at 2500 psi. Analysis of the pressure diagnostics for all strings indicates that the pressure source for the subject annulus is most likely a reservoir close to the 13-3/8″ shoe, traveling up the annulus via a “microannulus channel”. The observed pressure is very similar to the pressure expected in a reservoir at that depth.

Work Summary:

In October, 2002 a Seal-Tite® technician was mobilized to the platform. The procedure involved bleeding the annulus to zero and then slowly atomizing a customized blend of sealant into the annulus. Injection continued over the space of six days, interspersed by bleed-off periods to begin sealant activation. A total of 30 gallons of sealant was successfully injected into the annular area, at a maximum injection pressure of 2500 psi. Nitrogen pressure was left on the annulus to allow the sealant to cure.

After 3 days the pressure was released and the casing vented for one hour. A 7 day chart was placed on the casing to monitor the pressure increase. Over the course of 27 days the casing pressure slowly built back up to 1300 psi. This corresponds to the initial buildup rate of 3 hours, for a reduction of 99.5%.

In November 2002 a technician was mobilized to perform a second sealant application. The annulus pressure was again bled to zero. Additional sealant was then injected into the annulus and allowed to cure. The pressure was bled off and monitored. After 43 days the casing pressure of 75-300 psi has been observed to fluctuate according to thermal effects, which is expected due to a fluid packed annulus. No sustained feed-in has been recorded.

Conclusion:

The procedures developed and implemented by Seal-Tite® International have effectively sealed the microannulus channel in the subject wellbore.

High Island Area, Gulf of Mexico
The subject well had experienced a Sustained Casing Pressure (SCP) problem for several years in the
10-3/4” x 7-5/8″ annulus. Diagnostics indicated that the pressure source was most likely a zone at the 10-3/4” casing shoe, traveling to the surface via a microannular channel. When bled to zero, the pressure would increase to 1300 psi within 45 minutes, for an equivalent calculated rate of 7.6 MCF/day.

Seal-Tite® International developed and injected approximately 15 gallons of customized sealant, filling the microannulus to an estimated depth of over 1200 ft. Once the sealant was allowed to cure, the annulus was bled off and the pressure response recorded. The initial feed in rate was calculated to be only 0.042 MCF/Day, a reduction of 99.4%. A second sealant treatment of 20 gallons was then applied and the casing again bled to zero.

After 69 days the annulus pressure had built up to 825 psi. This corresponds to a calculated inflow rate of 0.023 MCF/day, a 99.9% reduction in the original inflow rate.

Background:

The subject well was completed in July 1978 with a TD of 8,316′. The casing program consisted of 26″ drive pipe, 16″ surface, 10-3/4″ intermediate, and 7-5/8″ production. The casing string characteristics are listed below:

Casing String Shoe Depth Burst Collapse Cement Info
26” 655 ft Drive Pipe
16″, 65#/ft H40 Butt 1,022 ft 1,640 psi 670 psi 850 sxs + 230 sxs grout
10-3/4″, 45.5 #/ft K55 Butt 4,500 ft 3,580 psi 2,090 psi 2359 sxs
7-5/8″ 26.4#/ft N80 LT&C 8,316 ft 6,020 psi 3,400 psi 2365 sxs, cement to surface

The first significant casing pressure on the 10-3/4″ x 7-5/8″ annulus was reported in 1988, with a reported pressure of 1665 psi. Standard “bleed and build” diagnostics indicated that the pressure would bleed to zero within 2 hours with an effluent of only gas. Within 12 hours the pressure would build back up to 1400 psi, eventually building to 1665 psi or 47% of burst pressure. Standard diagnostics performed in subse