Thursday 20 December 2012

Saltwater Disposal from Oil Wells in Oklahoma


Disposal of Produced Water from Oil Fields

Oil and natural gas exist, mixed with salt water in various proportions, in the porous underground rocks and shale.  Water is also injected during the process of hydraulic fracturing in natural gas wells such as Barnett Shale.  This water also comes out in different proportions when oil or natural gas is extracted. Most of the time, this extracted water is mixed with sand, polymers, oil, salt, clay and other dissolved materials.  The disposal of salt water, which is also called produced water, is a major concern during the production and processing of oil and natural gas.

There are various ways of disposing this extracted water.  In many cases, efforts are made to recycle a major part of it.  The process of recycling involves distillation or evaporation.  This is feasible only when there is constant flow and supply of water to keep the treatment plant working. Hence this method is adopted in places where there are several producing wells.  Even after recycling, a large amount of salt water and other solids remain for other methods of disposal.

In cases where this water comes from conventional reservoirs or oil, this water is injected back into the reservoir.   Another method of return of this salt water or oilfield brine is to inject it into under-ground porous rock formations which are not producing gas.  It is to be ensured that these rock formations are having impermeable and unbroken strata above and below.  These wells used for disposal has to adhere to the strict standards set by the Commission for disposal well construction, which includes casing with three layers.  These disposal wells are also inspected by Railroad Commission on a yearly basis.

The main purpose of these regulations is to ensure that there is no ground water contamination due to the disposal of oilfield brine.  In Texas about 50000 wells have been permitted for disposal of extracted water.  Though Barnett Shale Play, which is the largest natural gas plant in the state, has been operating since 1997, there have not been any instances of groundwater contamination due to water disposal so far in the area.

Tuesday 18 December 2012

The Oil Boom in Oklahoma


Optimistic Outlook for Oklahoma Oil Fields


There has been encouraging news from the latest tests being conducted in the oil fields in Oklahoma.  According to these tests, these oil fields, which is already the fastest developing ones in the world, may be containing considerably more oil than assessed earlier.

Continental Resources Inc., which has been conducting these tests, has already finished the probe test well into the rock layer which is underneath the Bakken Shale Field situated in Montana and North Dakota.  The results from the tests conducted in this oil field, which is already yielding producing oil, has been very heartening, according to company officials.  The company officials believe that the oil fields in Williston Basin might contain up to five layers of rock which may yield more oil and they are planning to conduct further tests.

Most of the 5000 salt wateroil wells in the area are drawing their production from the Bakken Shale layer, which is the uppermost, and Three Forks 1, which is below that.  The Continental’s latest well would be the first one to drill to Three Fork3 layer, whereas drilling of two wells into Three Forks 2 has already been completed.  The drilling of well to the deepest Three Forks 4 is planned to be done next year by the Oklahoma City Company.  However, the company officials are crossing their fingers about the final results from these explorations. Commercial saltwater disposal has also seen an increase in demand, as a large majority of wells bring up salt water as a byproduct. The increase in natural gas has also lead to a boom in gas wells and fracking efforts that produce large amounts of saltwater backflow.

The current prediction by Continental, based on the latest estimates in the lower Three Forks Rocks, is that these oil fields contain about 903 billion barrels of oil.  This is an increase of about 57% from the earlier estimates in 2012 that Bakken fields may contain about 577 billion barrels of oil.  Based on the calculation that 3 to 5 percent of oil can be recovered using latest technology, these fields may produce between 27 billion and 45 billion barrels.

The stock price of Continental has already felt the benefit of this good news coming from tests.  The stock price of the company gained by 4.2% when the news was announced and it is currently at the level of $81.60 in the New York Stock Exchange.

Monday 3 December 2012

What are Water Disposal Wells


The Need for Salt Water Disposal Wells


The porous underground reservoirs, where Oil and Natural gas is found, also contain water in different proportions.  Due to natural gravity, oil floats on this water and can mostly be extracted separately.  However, when oil or gas extracted, some of this salt water is also extracted along with it.  This natural salt water which comes along with targeted source is called produced water.  Water which is used for hydraulic fracturing to extract oil or gas also sometimes comes to the surface along with extracted materials. 

The purpose of water disposal wells is to return this extracted water to the deep sub terrain rock formations from which oil was extracted.  Such wells are also used for returning flow-back volumes from work-overs, which may include the water ejected from slick water-fracture.  This is the water or frack-fluid which is used for hydraulic fracturing of rock formations to release gas.
This type of water or fluid disposal needs to meet certain criteria, which is determined by the charecterstics of the rock formation.  The regulations for disposal of extracted water or fluids are administered by the Commission which is meant to protect the surface and underground water sources.  The method for disposal would depend on the various properties of the underground formations. The injection pressure and other methods are reviewed from time to time.

The permission for salt water disposal is granted by the Commission empowered by the Ministry of Environment.  This permission is issued after a thorough review of the application to ensure that the fluid migration to other areas from the injection zone is minimized.  It is necessary that the company has the right for extraction of petroleum and gas in the rock formation where the water disposal is done.  The Commission also issues an effluent permit for the composition of disposed water or fluid.  A monthly disposal or injection statement also has to be submitted to the Commission along with details such as average wellhead pressure and volume of disposed fluid.

Once the formalities are completed, the Commission, on behalf of Ministry of Environment, issues the approval for water disposal under the relevant Oil and Gas Activities Act.