Studi Magnetotelurik (MT) untuk Mendelineasi Potensi Regional Gas Serpih Bawah Permukaan Berdasarkan Properti Tahanan Jenis di Cekungan Kutai, Kalimantan Timur
DOI:
https://doi.org/10.33332/jgsm.geologi.v22i2.571Abstract
Telah dilakukan penelitian menggunakan metode magnetotelurik (MT) pada 40 titik lokasi pengukuran di sekitar Cekungan Kutai, Kalimantan Timur. Studi ini bermaksud untuk mengkarakterisasi keberadaan batuan induk untuk potensi gas serpih berdasarkan nilai tahanan jenis. Guna memperoleh gambaran kondisi geologi bawah permukaan yang baik, pengolahan data secara objektif dilakukan agar memperoleh kualitas data MT terbaik. Beberapa teknik pengolahan data seperti robust processing dan seleksi cross power (XPR) diaplikasikan untuk memisahkan komponen data dari gangguan sehingga memperoleh gambaran bawah permukaan yang dapat dipercaya dari kedalaman yang relatif dangkal hingga sangat dalam melalui tahap pemodelan inversi 2-D. Model inversi terdiri dari 3 penampang vertikal, yaitu penampang A-B, C-D dan E-F dengan arah relatif barat – timur yang memotong Antiklinorium Samarinda dengan panjang lintasan berturut-turut ±50 km, ±48 km dan ±32 km. Berdasarkan ketiga penampang vertikal tersebut, informasi sebaran anomali tahanan jenis rendah regional berhasil dipetakan yang selanjutnya ditafsirkan sebagai respon keberadaan batuan induk gas serpih di bawah permukaan. Pada penampang A-B, bagian atas lapisan konduktif ini diperoleh pada kedalaman yang bervariasi pada rentang kedalaman 1000-5000 m di bawah permukaan. Sementara itu, lapisan konduktif pada penampang C-D diperoleh pada kedalaman yang bervariasi dengan rentang 1500-7000 m di bawah permukaan, sedangkan anomali serupa pada penampang E-F diperoleh pada sekitar kedalaman 2000-3000 m. Variasi kedalaman lapisan konduktif ini ditafsirkan akibat adanya struktur geologi berupa patahan dan lipatan di sepanjang ketiga penampang vertikal yang tercermin dari adanya Antiklinorium Samarinda di permukaan.
Katakunci: Cekungan Kutai, gas serpih, magnetotelurik, tahanan jenis.
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