A Novel Approach for Near Wellbore Stimulation and Deposits Removal Utilizing Thermochemical Reaction

Organic and inorganic deposits play a major issue and concern in the wellbore of oil wells. This paper discusses the utilization of a new and novel approach utilizing a thermochemical recipe that shows a successful impact on both organic and inorganic deposits, as an elimination agent, and functions as stimulation fluid to improve the permeability of the near wellbore formation. The new recipe consists of mixing nitrite salt with sulfamic acid in the wellbore at the target zone. The product of this reaction includes heat, acidic salt, and nitrogen gas. The heat of the reaction is enough to liquefy the organic deposits, and the acidic salt will tackle the carbonate scale in the tube and will increase the permeability of the near wellbore area. The nitrogen gas is an inert gas; it will not affect the reaction and will help to flow back the well after the treatment. The experimental work shows an increment in the temperature by 65 °C when mixing the two chemicals. The test was conducted at room conditions and the temperature reached around 90 °C. Adding another 65 °C to the wellbore temperature is enough to melt asphaltene and wax, the acidic salt tackles carbonate scale. As a result, the mixture works on eliminating both the organic and inorganic deposits. The permeability of the limestone sample shows an increment of 65% when treated by the mixture of the reaction recipe. The uniqueness of the new thermochemical recipe is the potential of performing three objectives at the same time; the heat of the reaction removes the organic deposits in the wellbore, the acidic salt tackles carbonate scale, and improves the permeability of the near wellbore zone.

Development of a Methodology and Software Package for Predicting the Formation of Organic Deposits Based on the Results of Laboratory Studies

One of the main problems in the oil industry is the fallout of asphaltene–resin–paraffin deposits (ARPDs) during oil production and transportation. The formation of organic deposits leads to reduced equipment life and reduced production. Currently, there is no single methodology for the numerical simulation of the ARPD dropout process. The aim of our work was to obtain a correlation dependence characterizing the rate of wax growth over time for oils in the Perm Krai, depending on temperature, pressure, and speed conditions. Experimental data for 20 oil samples were obtained using a Wax Flow Loop installation that simulates fluid movement in tubing. The developed correlation was tested in 154 wells. The results of numerical modeling of the paraffin precipitation process made it possible to correct the inter-treatment period of scraping for 109 wells (71%), indicating the high accuracy of the developed approach.

Green Well Stimulation Fluids for Enhanced Oil Recovery from Tight Sand Formations: Field Wide 70+ Wells Study Over 4 Years

Legacy oil production from Appalachian basin has been in a decline mode since 2013. With more than 80% of wells producing less than 15 bbl/day, there is a growing interest in economically and environmentally viable options for well stimulation treatments. Analysis of formation mineralogy and reservoir fluids along with history of well interventions indicated formation damage in many wells due precipitation of organics and a change in wettability being partially responsible for production decline rates in excess of forecasts. The development and properties of a novel cost-effective biosurfactant based well-stimulation fluid are described here along lessons learned from several field trials in wells completed in the Upper Devonian Bradford Group. This group of 74 wells, completed in siltstone and sandstone reservoirs were presenting more than 12 well failures annually across the field, which was attributed to the accumulation of organic deposits in the tubulars. Based on these cases, batch stimulation treatments using a novel fluid comprising biosurfactants were proposed and implemented field wide. The treatments effectively removed organic deposits, changed formation wettability from oil to water wet and resulted in a sustained oil production increase. Well failures were significantly reduced as a result of this program and the group of 74 wells did not have a paraffin-related well failure for 18 months. Results from this program demonstrates the efficiency of the green well stimulation fluids in mitigating formation damage, reducing organics deposition and in increasing oil production as a promising method to stimulate tight formations.

Streets of Medieval Novgorod and GPR Search: Application Experience

Проблема реконструкции уличной сети средневекового Новгорода представляет собой один из ключевых вопросов городской исторической топографии. Традиционная методика опирается на комплексный анализ письменных, картографических и археологических источников, при этом решающим доводом остается физическое выявление уличной трассы в границах шурфа или раскопа. Технология георадарного поиска улиц опирается на характерную особенность уличных настилов: их периодическая замена формировала значительные вертикальные скопления древесины в мощном культурном слое. Применение георадара для поиска средневековых улиц позволило не только установить расположение трасс без вторжения в культурный слой, но и сформулировать комплекс проблем, связанных как с собственно технологией, так и с методикой археологической разведки по результатам предварительного анализа территории. Reconstruction of city street structure is one of the most important questions of medieval Novgorod topography. Traditional way of medieval street discovery is based on complex analysis of written sources, historical maps, and archaeological data. Ground penetration radar (GPR) technology allows to reveal constructions of wooden streets, buried in organic cultural deposits, which may reach several meters thick. GPR using allowed to locate position of several street pavements and raise several questions concerning both GPR usage on thick organic deposits and technology of archaeological exploration of medieval streets.

Isolation and Characterization of Cellulolytic Bacteria Diversity in Peatland Ecosystem and Their Cellulolytic Activities

Peatlands are terrestrial wetland ecosystems formed from piles of organic matter that decompose into organic deposits. Peat soil has a high potential to produce cellulose which, can be reused by cellulolytic bacteria. This study aims to find out the potential strain of cellulolytic bacteria isolated from peatland ecosystems. The method used was experimental, sequentially, the stages are isolation and screening for cellulolytic bacteria, quantitative testing of cellulolytic activity, characterizing the morphology and physiology of bacteria, and the identification of bacteria based on Bergey’s Manual of Determinative Bacteriology. The screening results obtained seven isolates of cellulolytic bacteria capable of hydrolysed cellulose on 1% Carboxy Methyl Cellulose (CMC) Agar Medium, namely SPS1, SPS2, SPS 3, SDG1, SDG 2, SPW1, and SPW4. Three of seven isolates obtained the highest cellulolytic index sequentially, namely SPS2 of 2.82, SPS3 of 2.65, and SDG1 of 2.47. The cellulolytic activity was indicated by the value of a halo zone around the colonies on 1 % CMC medium after being dripped with Congo red. The halo zone is an early indication to determine the ability of bacteria to decompose cellulose. Based on Bergey’s Manual of Determinative Bacteriology showed that the three isolates had the same characteristics as the genus Bacillus, Lactobacillus and Corynebacterium.

Improving the Efficiency of Oil and Gas Wells Complicated by the Formation of Asphalt–Resin–Paraffin Deposits

A number of difficulties may be encountered in the final stages of oil field exploitation, including the formation of asphalt–resin–paraffin deposits (ARPDs). It is expedient to use complex technologies to remove the already formed deposits and prevent the formation of ARPDs. This paper focuses on the complex technology of oil field exploitation. This technology combines both the removal of organic deposits and the prevention of the formation of these deposits in the well bottomhole formation zone (BHFZ) system. The calculations for determining the process parameters of selling the ARPD inhibitor solution into the BHFZ are presented in this article. This complex technology includes the process of ARPD removal by flushing the well and the subsequent injection of the developed ARPD solvent into the BHFZ. In addition, the technology is complemented by a method of preventing the formation of these deposits. This method consists of squeezing the ARPD inhibitor and then pumping it by the selling fluid from five to ten times of the volume. This article contains a detailed calculation of the methodology and provides the diagrams for the solvent and inhibitor injection.

The Choice of the Optimal Strategy for the Use of Solvents of High-Molecular Organic Deposits, Considering their Complex Composition and the Effect on the Oil Dispersion System

The long-term practice of operating wells producing oil rich in paraffins and asphaltenes has shown that the optimization of technologies for the removal of solid high-molecular organic deposits (asphaltene-resin-paraffin deposits) in oilfield equipment, lifting pipes and flow lines makes it possible to effectively solve the issues of improving the environmental friendliness and energy efficiency of oil production. The use of composite hydrocarbon solvents is one of the most well-known methods used to remove asphaltene-resin-paraffin deposits. Thus, to date, there is no systemic solution to this issue. This paper is aimed at discussing the provisions that determine the possible prospects for the development of an optimal strategy for the use of solvents for the removal of asphaltene-resin-paraffin deposits.

Achieving Uniform Fluid Distribution with a Custom-Designed Organic Solvent Maximizing Coiled Tubing Reach During Matrix Acid Stimulations

The success of stimulation fluid placement in openhole extended reach wells (ERWs) through coiled tubing (CT) is highly dependent on the depth achieved. Friction forces and helical buckling typically cause early CT lockup, which limits the reach. Organic deposits in the wellbore increases frictional forces causing premature lockup or in some cases even complete blockage. Efficient removal of organic deposits enables CT to reach maximum depth to perform the matrix stimulation. Analysis of these organic deposits was conducted and following a thorough comparative test, a new solvent-external phase emulsion inhibitor was selected to treat the wellbore prior to matrix stimulation. Optimum cleanout methodology was identified for the CT run with a high-pressure jetting nozzle (HPJN) combined with a chemical dissolution effect of the chosen solvent. Focused, high-energy fluid streams loosen any compacted deposits, while the high rate of fluid passing through the tool allows for an efficient cleanout. A matrix stimulation treatment with CT was then executed in the openhole section of the ERW with a TD of 18,773-ft (9800-ft horizontal lateral section) with HCl and emulsified acid systems. By using a solvent-external phase emulsion, only the external phase of the emulsion containing the dissolver is in contact with organic deposits; the remaining internal phase fluid is not. This therefore allows a reduction in total solvent volume. The proposed wellbore cleanout treatment with HPJN reduced the friction coefficient between CT and the completion by 10%. In turn, it was verified that during the operation, an additional 3,320 ft of reach was achieved in the openhole section. Combined with other extended-reach techniques (i.e., mechanical agitator tools, friction reducers), it allowed the 2.0-in CT pipe to reach the TD of the well (18,773 ft). These efforts together maximized the reservoir contact during the matrix stimulation in the openhole section with HCl and emulsified acid systems. Distributed temperature sensing (DTS) methodology was used with the aid of fiber optic installed CT, and the intake profile of the openhole section was mapped. Analysis of the data was applied to optimize the pumping schedule to obtain uniform production contribution across the openhole section. The systematic engineering workflow presented includes the organic deposit diagnostic procedure, laboratory testing, chemical selection, and treatment application. This yields a wellbore treatment that minimizes friction for the remainder of the operation and enables maximum CT reach. This provides more insights of integrated matrix stimulation treatment with CT to overcome the serious challenges present in extended reach openhole wells.

Influences of the Water Cut of Pumping Oil and the Mineralization of the Associated Water on the Rate of Sludging

The problem of the formation of organic deposits on the inside surfaces of borehole equipment and oilfield pipelines, which is urgent for all active oil fields, was considered in the study. The formation of these deposits leads to decreased lifespans for oilfield equipment and accidents involving oil pipelines and wells. The aim of our work was to estimate the dependencies of the organic deposition’s formation-rate factor on the water cut of the investigated water–oil emulsion and the mineralization of the water phase. Examination via generation of asphaltene–resin–paraffin deposits on the surfaces of cold rods was carried out with a “Cold Finger” CF-4 unit. Coefficients of specific oil sludging, fluid sludging and rate sludging have been determined. It has been defined that in the definite oilfields, the rate of sludging does not increase as the water content in the emulsion increases. As water-phase mineralization increases, this value remains practically constant.