Company visit

PERTAMINA EP FIELD, SUBANG & JATIBESAR

The recent activity that had been conducted by UISC AAPG is visiting to Seismic Survey and Drilling Well Operations in Subang – Karawang, West Java. This Operation is owned by PT. Pertamina EP and has been operated by PT. Elnusa Tbk, as the main Contractor. As planned before, this activity was held for two days one night with 20 students participated inside. This activity had also been organized and supervised by team of Pertamina EP and Elnusa directly.

The main objective of this acitivity was to learn a lot about seismic survey and drilling well operation have done in the real field. And by doing this activity we could learn everything that had been studied before in better way.

Day 1 – Seismic Survey Operation

As said before, this project is owned by PT. Pertamina EP with Mr. Yukha as the chief of operation field. And the main contractor, PT. Elnusa Tbk has Mr. Irwan as the team leader. This project is called 3D Land Seismic Survey – Akasia Bagus A5 89. To get the good data from 1012 km² field area along Subang, Majalengka, Sumedang, and Indramayu is the goal of this survey. So it could be well processed as the next stage of the operation at their main Office.

The information that we had got from field were that this survey is using two lines, shot line and receiver line. They use 54.090 shot points with 72 shot point lines and 66.576 receivers with 136 receiver lines. and they had recorded about 14.000 shot points at the time we came there. There are some stages from the beginning that must be done until getting the best data to be processed. They are : Pre-design – Scouting – Design Survey – Topography Survey – Bridging – Seismic drilling & preloading – Recording – Field processing.

1. Pre-Design

This is the earliest stage of the survey that has to be done before being implemented in a real field. This stage aims to make the earliest plan and design related to the survey before the observation to the survey area is done directly.

2. Scouting

You need expertise to thoroughly scout your new exploration block before preparing the Tender or the Contract. In some country or areas you will also need a serious security assessment.

3. Design Survey

This stage is the stage of planning. At this stage, all the important purposes related to the survey are discussed. For example, how many lines that will be used, how many shots point that will be used, how long the survey will be conducted, how many workers would be included, how the technical survey that will be executed, and several other important matters.

4. Topography Survey

The main purpose of this stage is to determine the points of seismic survey and to recontruct the coordinate of the theoretical result from the survey design to become the real measurement coordinate in the field. Mr. Ulung ,as the Topography Operator here, explained that Topography Survey is using some equipments, those are:

Total Stations Leica TC 1203.
RTK Trimble 4000 Ssi
GPS Trimble Receiver Dual Frequency
GP Seismic Software
Hand Held GPS

The data that will be got from here are the coordinate of angle and the latitude. And it was controlled by the sun shot from the sun.

5. Bridging

In this part, we build the track in the field to facilitate the mobilization of the survey’s equipments from base camp to the field. This stages is depending on the topography condition of the field.

6. Seismic Drilling & Preloading

After determining the points which would be observed, then the next step of this seismic survey system. That is an activity which is carried out by a special certified employee to assemble and perform charging those drill holes with an explosive source for each holes. Then, the holes that have been assembled will be secured and called Tamping. Here is the process of drilling system in seismic survey below

Fig 2. Seismic drilling System

Fig 3. Driling Process (left) and bit (right)

7. Recording

The recording is an activity to record the vibration signal ( sesmic signal ) which is coming from the sources which had been fitted previously in some areas. The result of this recording is called Raw Data. However, this activity is the most important of all seismic survey operation. This is because from this activity we could know which data could be processed and which one could not be. When the recording operator doing their job with the recording things, the man with his computer is ready for the data result from the vibration signal.

At night, we were explained about data processing software named MESA by Mr. Anggi from PT. Elnusa Tbk. MESA is a software which is used in this Seismic Survey Operations. It is used to make the design survey of this operation.

Day 2 – Drilling Well Operation

Here we are on the second day of Trip Division – UISC AAPG activity. In this day, we are got to know and learn more about drilling well operation from the real field. This drilling well site is located in Patrol, Jati Besar West Java. Based on the information that we had got, this well is going to be drilled for about 3400 metres depth. When we got there, the drilling process was already in about 400 metres depth and still have to work hardly to get their goal.

They used some equipments which has their own role in the drilling operations, such as mast/derrick, crown block, travelling hooke, travelling block, drilling line, deadline anchor, kelly bushing, muster bushing, and many more with their own roles in the drilling well operation.

There are several steps that must be done before starting the operation. Such as :