Hydrocarbon Domination

 

We could see where our most oil and gas reserves based on the largest O&G companies. 

But it's not always true where else many companies are taking the benefit from the other countries as wells in order to ensure their sustainability. And for that purpose, every country has their own regulation in order to allow such global companies to operate in a manner that suits the geological/political/economical aspect. 

     We take Qatar for example, economically it is showing a good growth in this recent years. As one of the OPEC members, it play a big role in determining the hydrocarbon economic environment. But instead of its good relationship with U.S. based companies, it states that foreign company would have to establish a jointventure with its partners plus limiting foreign ownership to not exceeding 49% of equity. While for companies to operate in country like Cuba, it would require non U.S. patented equipment to be bring in or they've allowed only certain pantenting percentage. As we would know, U.S. as well has put economic embargo on Cuba since 1960. Thus we could conclude that each country has their own regulation that need to be imposed in order to sustain own benefit in addition.

DST Overview

Being involve in exploration well drill stem test (DST) planning and operation provide a value and provide more appreciation on the reservoir engineering works.


Why do we need DST for exploration well? This would need to be agreed before the operation. But basic needs for exploration well is of course to get the reservoir properties of a newly discovered field. Hydrocarbon shows from the logs will dictate whether to go for a DST or not. Logs can only shows the presence of oil or gas in the reservoir, but whether it can be produced or not, we would need to flow it to surface to get confirmation. Then, we could collect the PVT fluid for the analysis especially when we would need quiet a volume of it.


How do we execute a DST then? We would need a proper planning before conducting DST, both on operation and test design (flowing sequence). Operationally, we would need to consider the personnel and equipment are all ready. If we talk about the offshore operation, we would need to ensure equipment are in very good condition and tested before being mobilized to the rig. On the test design, we would need to clarify our objectives in conducting the test. Plus, we need to agree in our team on the test sequence, how long we're going to flow the well plus the buildup period.

After the well reach the target depth, DST string will be lowered down into the well. Depending on type of testing, perforation would be commenced in cased hole testing or else open hole testing would be suitable for strong formation (normally basement reservoir). While run in hole, enough cushion will be fill up inside the string so that when the valve opened for flowing, it will prevent big surge of pressure (due to pressure difference at above and below the valve). Next, perforation will be done by the gun specialist at the correlated depth (by referring to the log).

Downhole tester valve will be open to allow for the first flow of the hydrocarbon to the surface. The well need a cleanup period in order to remove previously filled cushion fluid and remaining mud. After continuously stable hydrocarbon flow was established, next is to start the flow period for rate measurement and fluid sampling. The well will be shut in for the reservoir properties determination where the downhole gauge will ensure all the changes in pressure are recorded. As per previously said, the flow sequence and timing will be based on the specific objectives of the DST. An extended well testing is somewhat a different kind of DST which is flowed for a long period in order to assess the production sustainability.

What do we do with the result? Basically the surface data (rates, gas gravity, GOR, water cut) will be combined with the recorded downhole data (pressure and temperature) for the analysis which we called "pressure transient analysis". As the name suggest, pressure transient analysis is the evaluation of behaviour of the pressure propagation characteristic from the well to the formation. The analysis result will be suggest the well and reservoirs parameters (reservoir pressure, permeability, skin, wellbore storage, existence of nearby boundary, etc).

Man Made Disaster

We still remember the aftermath of Deepwater Horizon rig which kills 11 crews on board during the exploration drilling of Macondo. The blowout preventer failed to prevent the gas out which cause explosion and fire. It takes 3 months to put a temporary cap onto the well before confirmed on killing the well 2 months later with a relief well.

We give our best to contain the mistake we've done, but in reality our capacity is just limited. In this case, it is always better to learn from the mistake of others. After the incident, more consideration has been made on the drilling planning, especially on the well control part. Thus, worst case scenario are considered, even if it is to flow the well from the openhole section.

Matching the History

History matching is one of the important part in Reservoir Engineering. In conducting the task, as an engineer we would need to be very objective on the requirement. We need to ask first:-

1) What type of result we're expecting and for what purpose the result will then used for
2) Always talk to your boss, how much time do we have? so that we could have an agreement on when would be the delivery due. Also to prevent any unnecessary works especially when we know that it couldn't be delivered in time
3) Amount of data available and the confidence level we have on the data.

Only after considering all these checks then we could start doing the matching.

What is history matching basically & why do we run the history matching in the first place? Just like the stocks market, if we assume that not much parameters is changing through a period of time, we could estimate its future trend. Thus if the field operating condition got not much change throughout a period of time, we could use our observation until to date to predict the future performance of the reservoir. This is actually where the management will put most of their concern on especially when we're talking about the future recovery or the company future revenue.

Material balance or numerical simulation method are used for the matching of the pressures and production rates. Most of the time taken by the engineers is basically trying to experimenting with several reservoir and fluid parameters. In order to do the process efficiently, one would need to do it in a systematic way, or otherwise we could be stuck in the middle wasting much time trying to match every parameters. In my opinion, we should do it bottom up, doing the investigation of parameters starting from the reservoir to the surface. These are the recommended sequence of matching.

1) Bottomhole static reservoir pressure (BHP)
2) Oil rates
3) Water cut / the producing Gas-Oil Ratio
4) Tubing head pressure

Bottomhole pressures is more reliable to be used as a guide for the matching instead of trying the rates first, if enough data are available. This is because of we can rely on pressure measurement (most of today's pressure gauge is using the quartz gauge). But if we're talking about rates, there's possibility of measurement errors especially when measuring at the low production. That's why field data QC is important. We should be able to questioning its reliability when observing the anomalies by eyeballing through the profiles.

At the end of the day, when all the task was done and has been reviewed, we should be able to do economic analysis on our predicted profile and come out with a solution to improve the recovery through various possible methods (infill drilling, putting some injectors, Enhance Oil Recovery).

Being a Reservoir Engineer

It's already four (4) years since I've put myself in this position. And it's good to have a feeling that I'm progress in this field of petroleum engineering.
I've graduated in Mechanical Engineering, that's put me sometime in this arena wandering on whether I'm at the right position or not. New challenges, competition, hardtimes really makes me felt a bit disappointed looking at myself being behind compared to other Petroleum Engineering background colleagues during my early days in the organization. There's one time that i'm looking at myself that i would not be able to get myself up in the company. Seems like this might not be my dream job or at least not fit on my expectation.
There's a time where i've been asked by my superior whether i'd like to be transferred to other department that may suit me instead the position i'm in during that time. Maybe during the time, I seems not interested in improving my engineering knowledge. I delivered the job just for the sake of my salary or at least I got a things to do.
In the meantime, I trying on some part time job to fill up the emptiness within myself. Until a point where finally I realized that whatever I do, it's all up to what I believe it is. I couldn't excel in doing things if I still have the belief that what I do is wrong, or any decision I take is wrong.

I've started to understand that I have the responsibility to myself to keep me going, to any decision I made, and to things I'm doing. Only with that kind of thinking, I can focus on developing myself, and get to wherever I want to be and whoever I want to become.

Things went very fast. And right now I'm so sure that I hold my own destiny. To become an excellence reservoir engineer is my priority. To contribute to the people and my own country is my mission. My vision is then to bring the company to another level of success. Thanks to the people surrounding me, who always shows good examples, bring good deeds, and inspire me to become what I'm today, a RESERVOIR ENGINEER.