ANALISA MEKANISME PENDORONG RESERVOIR “AB” FORMASI CIBULAKAN BAWAH CEKUNGAN JAWA BARAT UTARA

Authors

  • Bagus Adhitya Universitas Jambi
  • Hari Wiki Utama

DOI:

https://doi.org/10.22437/jop.v6i1.10430

Abstract

Abstrak

Mekanisme Pendorong reservoir maksudnya adalah jenis tenaga pendorong yang berasal dari formasi reservoir. Tenaga pendorong ini berperan untuk memproduksikan minyak dari reservoir masuk ke lubang bor dan naik kepermukaan tanpa bantuan pompa. Namun energi pendorong ini tidak akan bertahan sampai akhir produksi suatu lapangan, karena seiring dengan proses produksi fluida reservoir ke permukaan, akan terjadi pengurangan tekanan sehingga tenaga pendorong alami hanyak akan bertahan pada saat tahap primary recovery atau pada saat Pwf (well flowing pressure) lebih besar dari Ps (static pressure). Mengetahui jenis mekanisme pendorong ini akan membantu dalam mengetahui berapa lama tahap primary recovery ini berlangsung sehingga perencanaan proses produksi akan semakin baik, dan juga dengan mengetahui jenis mekanisme pendorong ini akan membantu dalam proses simulasi reservoir agar model dinamis yang dibuad akan merepresentasikan reservoir yang sebenarnya. Terdapat 5 jenis mekanisme pendorong yang bekerja pada suatu reservoir, meliputi: depletion drive, gas cap drive, water drive, gravity drainage drive, dan combination drive.

Untuk mengidentifikasi jenis mekanisme pendorong yang bekerja pada suatu reservoir dapat dilakukan dengan metode kualitatif dan metode kuantitatif. Pada metode kualitatif dengan menganalisa trend produksi minyak, air, gas, water cut, GOR, dan tekanan reservoir. Dari trend yang terbentuk akan diketahui bagaimana karakteristik reservoir berdasarkan mekanisme pendorong yang bekerja. Pada metode kuantitatif dilakukan analisa Drive Index untuk menentukan mekanisme pendorong yang bekerja pada suatu reservoir. Dari hasil analisa kualitatif dan kuantitatif diketahui mekanisme pendorong yang bekerja pada reservoir AB adalah combination drive, yang merupakan gabungan dari depletion drive dan weak water drive. Justifikasi weak water drive pada reservoir AB dikarenakan nilai RF (recovery factor) sampai akhir produksi baru mencapai 15.2%, yang artinya masih ada cadangan minyak yang tersisa sebesar 84.8% di reservoir AB.

Reservoir AB berada pada Cekungan Jawa Barat Utara, Anggota Formasi Cibulakan Bawah. Berdasarkan ciri korelasi litologi dengan Cekungan Sumatera Selatan Anggota Formasi Cibulakan Bawah ini terdiri dari setara Formasi Talangakar dan Setara Formasi Baturaja, dan untuk reservoir AB ini termasuk kedalam setara Formasi Talangakar. Dari analisa fosil diketahui Formasi Talangakar berumur Miosen bawah, dan dari analisa coring formasi ini diendapkan pada lingkungan transisi dibuktikan dengan perselingan serpih, batupasir, dan batugamping dengan sisipan napal, batulanau, dan batubara. Formasi Talangakar ini adalah formasi yang sangat penting di Cekungan Jawa Barat Utara karena berperan sebagai source rock, reservoir rock, dan cap rock.  

Kata Kunci: Mekanisme Pendorong; Formasi Talangakar; Cekungan Jawa Barat Utara

Abstract

Reservoir Drive mechanism means the type of natural driving force that origin from the reservoir formation. This driving force plays a role in producing oil from the reservoir into the borehole and rising to the surface without the aid of a pump. However, this driving energy will not last until the end of a field's production, because along with the production process, there will be a reduction in pressure so that the natural driving force will only last during the primary recovery stage or when the Pwf is higher than Ps. Knowing the type of driving mechanism will help in knowing how long this primary recovery stage will occurred, so that planning the production process will be preferable, and it will help the dynamic model that is created will represent the real reservoir. There are 5 types of drive mechanisms that act on a reservoir such as; depletion drive, gas cap drive, water drive, gravity drainage drive, and combination drive.

Qualitative and quantitative methods can be used to identify the type of drive mechanism that act on a reservoir. Qualitative methods used by analyzing the production trends of oil, water, gas, water cut, GOR, and reservoir pressure. It will be known how the reservoir characteristics based on the driving mechanism from the trend formed. In quantitative method, Drive Index analysis is carried out to determine the drive mechanism that acts on a reservoir. From the results of qualitative and quantitative analysis, it known that the driving mechanism that works on reservoir AB are combination drive, which is a combination of depletion drive and weak water drive. The justification for the weak water drive in reservoir AB is due to the RF (recovery factor) at the end of production only reached 15.2%, which means there is still 84.8% remaining oil reserves in reservoir AB.

Reservoir AB is located in North West Java Basin, member of the Lower Cibulakan Formation, based on the characteristics of the lithological correlation with the South Sumatra Basin. Reservoir AB is included in the equivalent of the Talangakar Formation. From fossil analysis, it known that the Talangakar Formation aged lower Miocene, and from the coring analysis this formation is deposited in transitional environment as evidenced by interlude shale, sandstone and limestone with inserts of marl, siltstone, and coal. The Talangakar Formation is very important formation in the North West Java Basin because it acts as source rock, reservoir rock, and cap rock.

Keywords: Drive Mechanism; Talangakar Formation; North West Java Basin

 

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References

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Published

2020-10-31

How to Cite

Adhitya, B., & Utama, H. W. (2020). ANALISA MEKANISME PENDORONG RESERVOIR “AB” FORMASI CIBULAKAN BAWAH CEKUNGAN JAWA BARAT UTARA . JOURNAL ONLINE OF PHYSICS, 6(1), 1-5. https://doi.org/10.22437/jop.v6i1.10430