Stimulation is performed on a well to increase or restore production. Sometimes, a well initially exhibits low permeability, and stimulation is employed to commence production from the reservoir. Other times, stimulation is used to further encourage permeability and flow from an already existing well that has become under-productive.
A type of stimulation treatment, acidizing is performed below the reservoir fracture pressure in an effort to restore the natural permeability of the reservoir rock. Well acidizing is achieved by pumping acid into the well to dissolve limestone, dolomite and calcite cement between the sediment grains of the reservoir rocks. There are two types of acid treatment: matrix acidizing and fracture acidizing.
A matrix acid job is performed when acid is pumped into the well and into the pores of the reservoir rocks. In this form of acidization, the acids dissolve the sediments and mud solids that are inhibiting the permeability of the rock, enlarging the natural pores of the reservoir and stimulating flow of hydrocarbons.
While matrix acidizing is done at a low enough pressure to keep from fracturing the reservoir rock, fracture acidizing involves pumping highly pressurized acid into the well, physically fracturing the reservoir rock and dissolving the permeability inhibitive sediments. This type of acid job forms channels through which the hydrocarbons can flow.
There are different acids used to perform an acid job on wells. A common type of acid employed on wells to stimulate production is hydrochloric acids (HCI), which are useful in removing carbonate reservoirs, or limestones and dolomites, from the rock. Also, HCI can be combined with a mud acid, or hydrofluoric acid (HF), and used to dissolve quartz, sand and clay from the reservoir rocks.
In order to protect the integrity of the already completed well, inhibitor additives are introduced to the well to prohibit the acid from breaking down the steel casing in the well. Also, a sequestering agent can be added to block the formation of gels or precipitate of iron, which can clog the reservoir pores during an acid job.
After an acid job is performed, the used acid and sediments removed from the reservoir are washed out of the well in a process called backflush.
In 1959, technology was being developed to pump liquid oxygen as a fuel source for the United States missile industry and space program. In order to pump this supercold liquid, cryogenic pumps, capable of handling fluids as cold as -350 F, were developed. In turn, these new pumps enabled Big Three Industries, a large producer of liquefied industrial gases, based in Houston, Texas, to sell more of their product, liquid oxygen. In producing this liquefied oxygen, large amounts of the by-product nitrogen were also produced, for which there was little use at the time.
Liquid nitrogen is a free-flowing liquid which is lighter than water, 6.738 pounds per gallon, and very cold, -320 F. Discoveries were made, however, that liquid nitrogen pumped under immense pressure could be used in oil production for displacement, backwashing and other well cleaning and stimulation applications.
Because nitrogen is colorless, odorless, and inert, it could be used in numerous applications without fear of contaminating the well. The new generation cryogenic pumps allowed implementation of a range of nitrogen services and produced a profitable application for the by-product of the Big Three oxygen plants, nitrogen. Mr. A. W. (Smitty) Smith, an oilfield worker from Louisiana, was the individual who approached Big Three Industries with the idea of incorporating liquid nitrogen in oilfield applications. Prior to this, compressed nitrogen gas in tubes or cylinders was the only source of gaseous nitrogen energy and it had some obvious disadvantages: maximum pressures of 2400 psi and rapid depletion of supply. A. W. Smith’s new low-temperature concepts were translated into equipment, procedures and supplies, and on December 17, 1959, in Liberty County, Texas, the first job was performed. It was the first of many successful operations and from 1959 to 1962, Big Three expanded their oilwell services through their wholly owned subsidiary called Nitrogen Oil Well Service Company, operating primarily in the Gulf Coast are of Texas and Louisiana. It didn’t take long for news of these developments to reach oilfield personnel in Canada.
Recognizing the value of this development, people began urging Mr. Harry K. Smith, President of Big Three Industries, to expand his nitrogen oilwell services to Canada.
Coiled tubing operations have been used since the 1960’s for simple pumping operations such as nitrogen kickoffs. Nowsco services along with Big Three Industries and in conjunction with Bowen Tools (wholly owned subsidiary of Big Three) developed the first coiled tubing units. These first units were developed to enable Nowsco to pump more nitrogen in well unloading applications. In fact, Nowsco was awarded a US patent for the process of pumping nitrogen through COILED TUBING and charged the industry .04 cents per/100SCF pumped for years. During the early development, COILED TUBING suffered a poor service quality due to tubing failures at the well site. Nowsco however, had developed the COILED TUBING strings with Quality tubing (another wholly owned subsidiary of Big Three) that were far superior to any other manufacturer from the 1970’s forward. In the mid-1980s, there was a dramatic improvement in the quality of the COILED TUBING with the availability of improved materials due to Competition coming in and several other manufacturers. As the reliability of COILED TUBING increased, new COILED TUBING applications have developed which are more demanding on COILED TUBING than the simple pumping operations mentioned above.
COILED TUBING has become an integral component of many work over and well intervention operations (During production phase of the oil well, there are a number of problems that can occur which will negatively affect operations, production and ultimately revenue generated, such as failure of mechanical equipment, changes in production characteristics, plugging and increases in injection pressure., these events may occur, requiring modification of the well in order to achieve optimal production) Coiled tubing use in these instances can limit the above issues with marginal cost.
While well service/work over applications still account for more than 75% of COILED TUBING use, technical advancements have increased the utilization of COILED TUBING in wide applications like drilling, completion operations, sand cleanouts, acidizing, fracturing, well testing, perforating, and other remediation activities are combined with the speed and convenience of COILED TUBING to provide even more benefit to well productivity.
According to industry experts, COILED TUBING use continues to grow at an average rate of 3.5% per year, and many oil and gas producers routinely use COILED TUBING techniques not only to remediate failing wells but also to complete new wells in a cost-effective manner. Many companies are aggressively developing equipment that leverages the multiple benefits of such activities and provides oil and gas producers with cost-effective alternatives.
Snubbing is a process that controls the pressure of oil or gas in order to run or pull tubing, drill pipe, or casing without performing a kill procedure of the well. Quick Jacks applications use the standard snubbing unit to complete or re-
Snubbing is versatile alternative that can overcome the limitations of other workover systems -
Snubbing is also a faster solution. Snubbing units can often have the task completed before a conventional workover operation is even rigged up.
Snubbing is your best choice when conventional draw works are absent. The self-