In gravel pack method, sand is used to hold the formation sand & preventing it from coming in into the wellbore. Then a screen is needed to hold this gravel pack sand in place. In fracturing, sand (aka proppant) is used to hold the fractures open & preventing it from closing in after we stop the pumping.
Sand/proppant size is controlled by the formation sand size. Once we know the size of the formation sand, we can use different methods to determine the required size of the sand/proppant. The most popular one is the Sacier method. Others are Schwartz, Stein, Hill & Coberly methods. The sand/proppant size is bigger than the formation sand size. How much bigger, depends on what method are you using. 20/40 sand has grain diameter ranging from 0.0165 to 0.033in. 40/60 sand:
0.0098 to 0.0165in. 40/60 sand is used if the formation sand is finer relatively to 20/40 sand.

Tanya – Adhia Utama Jauharuddin Madhan

Bapak2 dan Ibu2 yang terhormat,

Perkenankan saya yang sangat awam ini meminta sedikit penjelasan…
Saya ingin tahu kegunaan gravel pack sand dan fracturing sand dengan standar API RP 58 dalam oil industry. Trus, GPS ini punya dua jenis 20/40 dan 40/60, Bisa dijelaskan perbedaan kegunaannya? Kalau dilihat memang ukuran mesh-nya berbeda tapi saya ingin tahu perbedaan kegunaannya.
Kebetulan saya punya barangnya dan saya ingin lebih mengetahui kegunaannya (maklum anak ingusan yang baru belajar E&P-red).

Tanggapan 1 – Doddy Samperuru

Dear Pak Adhia,

In gravel pack method, sand is used to hold the formation sand & preventing it from coming in into the wellbore. Then a screen is needed to hold this gravel pack sand in place. In fracturing, sand (aka proppant) is used to hold the fractures open & preventing it from closing in after we stop the pumping.
Sand/proppant size is controlled by the formation sand size. Once we know the size of the formation sand, we can use different methods to determine the required size of the sand/proppant. The most popular one is the Sacier method. Others are Schwartz, Stein, Hill & Coberly methods. The sand/proppant size is bigger than the formation sand size. How much bigger, depends on what method are you using. 20/40 sand has grain diameter ranging from 0.0165 to 0.033in. 40/60 sand:
0.0098 to 0.0165in. 40/60 sand is used if the formation sand is finer relatively to 20/40 sand.

Tanggapan 2 – Adhia Utama Jauharuddin Madhan@elnusa

Thank you for all the comments and answer…

For further question, I need to ask several question about hydraulic fracturing…

* Hydraulic fracture is formed when a fluid is pumped down the well at high pressure for short periods of time (mainly hours). Why it’s only for short periods of time?

* What is ‘hydraulic fracturing in situ stress’?

* Usually sand carried by the high viscosity additives into the fractures to keep them from closing when the pumping pressure is released. What kind of additives that is used to carry the sand?

May be that’s all for now and I can assure you I will ask more and more question about E&P until I get everything…

Tanggapan 3 – Doddy Samperuru

Dear Pak Adhia,

At 03:03 PM 3/15/2004 +0700, Adhia Utama Jauharuddin Madhan wrote:

For further question, I need to ask several question about hydraulic fracturing…

* Hydraulic fracture is formed when a fluid is pumped down the well at high pressure for short periods of time (mainly hours). Why it’s only for short periods of time?

I think you are referring to pumping time, which is determined by job design (volume of fluids & slurry, rate of pumping, the geometry of fractures, perforations depths, size of tubings, etc.). In DSF (Duri Steam Flood) & Kern River field, for example, pumping time is only less than an hour & the total fluid volume is roughly a couple of thousand gallons. In deep HPHT gas wells in Texas, pumping time is usually more than three hours & the volume could be more around 50,000 gallons.
The basic idea is, we pump fluids down the tubing into the perfs, we frac the formation with the fluids (some fluids loss into the formation), we fill the fractures with the proppant gradually until it reaches the optimum density, then we stop pumping. Wait until the fractures stabilize. From here we can see that the overall time depends on many factors.

* What is ‘hydraulic fracturing in situ stress’?

This is pressure from the surrounding formation rocks which acting onto the fractures. It tends to keeping the fractures closed. It controls the geometry of the fractures. In order for us to be able to propagate the fractures, we must overcome this pressure. Once it’s done, we need to put proppant inside the fractures so it will be kept open.

* Usually sand carried by the high viscosity additives into the fractures to keep them from closing when the pumping pressure is released. What kind of additives that is used to carry the sand?

The correct terms will be ‘…. sand carried by the high viscosity fluids into the fractures…’. The fluids consist of gelling/viscosifier agent, water & different additives. Additives are chemicals to control one or more properties of the fluids. There are more than one hundred type of additives. There were some discussions about these fluids previously in this milis.