Page 38: of Offshore Engineer Magazine (Sep/Oct 2022)

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TECH FEATURE PRODUCTION OPTIMIZATION

RETROFITTING AUTONOMOUS

INFLOW CONTROL DEVICES

OFFSHORE CHINA

By Mojtaba Moradi, Jingheng Hau and Michael Konopczynski,

Tendeka and Ling Dai et al, CNOOC China Ltd ater breakthrough in a horizontal well is duced daily, including 1,885 barrels of oil with water cut of often the result of varying reservoir prop- 21.8%. After one week, the water cut exceeded 40% and af- erties, layer pressure, and fuid contacts in ter one month reached 60% and decreased rapidly after that.

Wzones intersected by the well. While in- The results of running PLT showed that the water rapidly fow control devices (ICDs) can be used to mitigate and broke through the high permeability zones and the horizon- manage the reservoir fuid infux toward the wellbore, the tal section was unevenly produced even with installed ICDs. technology is unable to adapt to the dynamic change in the As the crude oil viscosity of the producer well was 18.7cp, reservoir if there is a high mobility contrast between the there was still residual oil around the well, and the remain- viscous oil and water. In addition, successful water produc- ing recoverable reserves was estimated to be 69,000m3, the tion control with ICDs requires isolation in the annulus implementation of AICDs was considered to improve the between the formation and the wellbore1&2. well performance. AICDs were introduced to function as

During an intervention campaign in the Pearl River standard ICDs prior to the breakthrough (proactive solu-

Mouth Basin of the South China Sea, CNOOC aimed to tion). It limits the production of unwanted effuents with improve production by retroftting a horizontal well located lower viscosity after breakthrough such as gas in light oil about 120km southeast of Hong Kong. Water mobility in and both gas and water in heavy oil production (reactive the reservoir was at least 20 times higher than oil mobility solution). It is a viscosity and density-dependent device and a strong aquifer was located below the well. The well which is typically incorporated as part of a screen joint as was drilled along a heterogeneous formation with varying shown in Figure 1. For retroft applications, an inner string properties resulting in an uneven reservoir infux toward consisting of AICD subs and swellable packers is installed the wellbore. Although the well was already completed with within the existing wellbore. In this case, compartmental- passive ICDs, within a couple of weeks of starting produc- ization is driven by the existing wellbore, whether that be tion, the well suffered from severe early water breakthrough. standalone screens or gravel-packed completion along with

Global production optimization specialist, Tendeka, was packers for zonal isolation as shown in Figure 2, or with contracted to perform an integrated study comprising history cased and perforated wells. If extra compartmentalization matching and performance evaluation of the existing comple- is required, chemical annular isolations can be used. tion. Sensitivity analyses were used to determine the best retroft Flow loop testing was performed to check AICD func- completion for the well using autonomous ICDs (AICDs) to tionality where single-phase oil and water, and multiphase ensure a balanced contribution from all reservoir sections. The samples were fowed through the AICD to evaluate its per- bi-stable devices can control the reservoir fuid infux toward formance. Under 500kPa differential pressure, the single- 3-5 the wellbore while signifcantly limiting water production . phase oil fow rate through the AICD is about 1m3/h, which is about 5.5 times higher than the fow rate of sin- gle-phase water. For multiphase oil-water mixtures under

Retroft application

A well with a horizontal length of 536m was drilled in a the same pressure difference, the higher the water cut in thin formation with the oil column averaging 5m. In the the oil-water mixture, the smaller the fow rate through the

AICD. Several other tests with other fuids with viscosity initial production phase, 2,411 barrels of liquid were pro- 38 OFFSHORE ENGINEER OEDIGITAL.COM