Evaluasi Pekerjaan Squeeze Cementing Pada Lapisan High Permeability Reservoir Di Sumur AX-11 Lapangan Tal
u mur AX-11 merupakan sumur lepas pantai penghasil minyak di Lapangan Tal yang memiliki kedalaman 4955 ft-MD dengan porositas dan permeabilitas yang tinggi, yaitu sekitar 20 - 25% dan 100 mDarcy yang dapat mengindikasikan adanya zona loss. Sumur AX-11, mulai beroperasi pada Januari 2023. Tetapi dari produksi selama 3 bulan, terjadi produksi air yang sangat besar yang ditandai dengan watercut sebesar hampir 99%. Nilai watercut yang besar dicurigai karena adanya kemungkinan semen mengalami channeling dan air formasi ikut terproduksikan. Oleh karena itu dilakukanlah noise log yang akan memperlihatkan ada atau tidaknya channeling di belakang casing. Noise log dilakukan dari kedalaman 4000 hingga 4955 ft-MD menggunakan ALFA TEMP CCL yang kemudian dikorelasikan dengan hasil pembacaan cement bond log (CBL) dan variable density log (VDL). Dari hasil pembacaan tersebut terlihat bahwa terdapat channeling di belakang casing, sehingga sumur ini kemudian akan ditutup pada zona perforasi dan dibuat zona perforasi baru. Zona perforasi lama ditutup dengan squeeze cementing pada kedalaman 4622 hingga 4648 ft-MD. Jenis semen yang digunakan pada pekerjaan ini adalah semen kelas G dengan metode squeeze cementing menggunakan coiled tubing. Setelah dilakukan injectivity test, kegiatan cementing dilaksanakan sebanyak 3 kali dikarenakan adanya loss pada percobaan pertama dan teknik yang dilakukan pun berbeda. Pada re-cementing, dilakukan lay in setelah squeeze 5 bbls pertama dengan harapan sisa dari semen yang dikirim setelahnya dapat menempati celah-celah yang tidak ditempati oleh semen pada pemompaan pertama. Digunakan beberapa jenis additives pada pencampuran semen seperti: D-Air, CFR-3L, HALAD-413L, silicalite liquid, SCR-100L, dan fresh water. Kemudian dilakukan milling semen (drill out cement) untuk dilakukan Injectivity test terakhir kali dan di-run CBL. Hasil running CBL ini kemudian memperlihatkan hubungan cement-to-casing dan cement-to-formation. Kegiatan cementing dianggap berhasil ketika tekanan saat injectivity test dapat hold pada waktu yang diinginkan, di mana artinya semen tersebut tidak bocor atau loss ke formasi.
W ell AX-11 is an offshore well located in TAL field which has a depths of 4955 ft-MD with high permeability and porosity, which are around 20-25% and 100 mDarcy continuously. It is to be said that there is an indication of loss due to its permeability and porosity. This well has been operated since January 2023. However, after 3 months of production Well AX-11 has a really high produce of water (water cut) almost 99%. This event brought up an assumption that there is possible channelling behind casing. Therefore engineer has proposed running noise log and squeeze cementing to close the perforation zone and fix the channelling. Noise log performed at depth 4000 to 4955 ft-MD using ALFA TEMP CCL which will be correlated with cement bond log (CBL) and variable density log (VDL). The result of noise log had shown that there is a channelling along the casing in the perforation zone so it is concluded to perform squeeze cementing. Squeeze cementing performed at depths of 4622 ft-MD to 4686 ft-MD. G class cement was being used for this job while using coiled tubing method as the method of squeeze cementing. Once injectivity test has been performed, it is followed by pumping cement. Cementing had to be done 3 times for there was loss on the first try of cementing. At re-cementing stage, the cementing had to be done with different technique, which is by injecting some cement then let the cement lay in the wellbore and then start to let the cement drip from the coiled tubing with expectations, the dripped of cement could fill the spaces that hasn’t been filled by the first pump. There are some additives added to the cement which are: D-Air, CFR-3L, HALAD-413L, silicalite liquid, SCR-100L, and fresh water. Before injectivity test and CBL being run, the cement was being drill out (milling cement). The result of CBL shown cement-to-casing bond and cement-to-formation bond. A cementing job considered success as the pressure when injectivity test is conducted hold for a some certain minutes which means there are no leak or loss.