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Brenntag introduces new salt inhibitor for low-pressure gas wells
Posted: 19 September 2005
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Brenntag, one of the leading chemical distributors worldwide, has developed the T-3000E salt inhibitor to prevent salt deposition in low-pressure gas wells. The new product, which consists of a concentrated blend of proprietary water-soluble and biodegradable compounds, offers a preferred alternative to flushing warm water during production because it saves valuable production time and secures the economy of a well.
Precipitation of salt (sodium chloride, NaCl) is a serious problem and can  block the flow path of hydrocarbons. Salt scaling is particularly severe in wells with high saline (>200 g/l), forming brines, or brines near saturation with respect to sodium chloride. This phenomena occurs more frequently in gas wells than in oil wells and is caused by low pressure and decreasing temperatures.
Mature reservoirs usually have low pressure in the perforations, tubing nipples or chokes. When gas and salt water are retrieved from these reservoirs, more water vapor is taken from the well fluid than salt. The over saturation may be accelerated if the fluid is cooled down during production from the well bore to the surface or when transporting from the wellhead to the transfer lines. The cubical crystal structure of salt and its easy crystal formation allow growth of a dense salt network. In addition salt crystals adhere very easily to uneven surfaces, often found in production tubing and chokes.
At first glance this seems a minor problem, which can be solved easily by flushing warm fresh water on a regular basis. However, if this occurs on a daily basis, valuable production time will be lost and the reliability as well as the profitability of the well will become doubtful.
Brenntag’s T-3000E modifies the crystal orientation of salt from symmetric cubic to random dentric crystals. This has two implications: first it takes longer to grow crystals and secondly the formed random crystals do not block the flow path. This unique property provides many advantages; it delays salt deposition and prevents the formation of a hard plug. Instead, pumpable salt slurry is formed, which can easily be flushed from the well bore. This treatment will therefore prolong the time in between cleanouts and increase production time.
Case study Salt Plug removal
Well description
A problem was identified for a gas producing (100 liter water/ day) well containing salt in the oil and water phase. The well in question has a depth of approx. 3,5 km with a 2 7/8 production tubing. The reservoir is dolomite. The wellhead temp is 15°C, the bottom temperature is 100°C. Operational pressure is 70 bar. The crude oil has a density 0.831kg/l, with a viscosity: 3.502 cP. The gas contains H2S: 151 mg/dm3, chlorides: 44.5 mg/dm3, paraffins: 6 % mass and sulphur: 0.88 % mass.
The challenge
The water analysis showed a high concentration of 120 gram/l (300 gram is saturated) salt. Samples of the plugging material were analyzed and showed about 95% NaCl and some other salts. Based on these figures the preliminary conclusion of Brenntag was that the tubing of the well and the flow line were plugged with salt.
Customer was interested in the Brenntag Solution for the deplugging of the salt blockage using.
The Solution
Plant personnel prepared 500 liters of a treatment fluid, containing T-3000E, salt inhibitor and TDL-12E, wetting surfactant. The first step consisted of injecting approximately 100 liters of the T-3000E solution using high-pressure pumps to build up the pressure to 150 bars. In 30 minutes time the pressure dropped to 70 bars. During the next 24 hours additional treatment fluid was injected to keep the pressure on 150 bars. After soaking for 5 days the pressure dropped to 70 bars again, which led to the conclusion that the plug was (partially) removed. The customer decided to verify the effectiveness of Brenntag’s T-3000E solution by using a mechanical de-plugging method. Although some remains of the salt plug were retrieved mechanically it could be concluded that the plug was removed.
Conclusion:
Salt crystals / salt plugs can be (partially) dissolved or removed by the T-3000E salt inhibitor. Pumping in T-3000E solution against the pressure of the well is not easy but can result in dissolving of the salt plug. Care needs to be taken as movement of the salt crystals / plug can cause other obstructions down stream of the initial position of the plug.
In conclusion it is recommended to apply continuous dosing of T-3000E solution as a precaution as this will avoid build up of salts in the first place. Field trials and additional experiments applying a variety of doses T-3000E are currently running to prove the effectiveness of the T-3000E salt inhibitor.
Brenntag is the foremost chemicals distributor in Europe and recorded sales of Euro 4.6 billion in 2004 through the efforts of 8,900 employees at 300 locations worldwide. The Brenntag Oil & Gas Team manages a full line of products and services to the oil and gas producing and processing industries. Brenntag has been an important player in the oil and gas industry in North America and Canada and is actively working on expanding its presence in Europe . From their office in Dordrecht , The Netherlands, a dedicated team of technicians supports the Brenntag sales organisations throughout Europe .
In addition to T-3000E, Brenntag delivers a variety of chemicals with functions varying from base chemicals to process assisting chemicals as well as chemicals that are used for preventive maintenance and system and pipeline cleaning products & services. Thanks to a fine grid of Brenntag office and warehouse locations all over Europe , local services, knowledge and the access to nearly all conceivable chemical products, Brenntag is a favorable partner for the oil and gas industry.
Posted by Editor Pipeline Magazine
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