An attempt has been made in this work to formulate a novel water based mud system with acrylamido-methyl-propane sulfonate polymer (AMPS) grafted clay/CuO nanocomposite for drilling the high temperature troublesome shale formations. Literature survey found several water mud applications of AMPS polymers in the high temperature and high salinity environment as they are highly water-soluble anionic additives. On the other hand, investigators have reported very encouraging results on rheology and fluid loss control, shale impact, well bore stability and strengthening, cuttings lifting capacity and suspension and impact on thermal properties with CuO nano particle. The improvement in rheological and fluid loss control can be attributed to the fact that pore size studies on shales have suggested nano pore size of 2-50 nm. Conventional shale stabilizers and polymers contained in a water based mud cannot plug nanopores of shale. Therefore, water invades into the wellbore, and results in high mud filtrate volume and clay swelling. Given above, AMPS grafted clay/CuO nanocomposite is expected to improve on the CuO nano particle (NP) performance and provide an excellent solution to plug nano pore size of the shale. Hence, in this paper we tried to develop a synthesized additive which assists the drilling mud to provide better bore hole stability and well integrity while drilling the formations.
Acidizing treatments are the primary technique to enhance production of carbonate formations. Analysis of historical matrix treatment flowback, and laboratory assessment provide insights on the reservoir response to the acid recipe, and thus, positively enhance the selection of fluid recipes. The objective of this paper is to share an evaluation method to assess the effectiveness of an HCl-based acid recipe through experimental studies and flowback analysis.
Gelled, emulsified, and straight hydrochloric acids (HCl) were used to demonstrate the method. Inductively-Coupled Plasma (ICP) was utilized to characterize the liquid flowback samples. HP/HT filter press test was conducted using oil-based and water-based drilling fluids at 150°F to examine the integrity of filter cake and the removal means. Compatibility between crude oil sample and the acid recipe was conducted under reservoir conditions using HP/HT aging cell. ICP analysis was used to correlate the calcium concentration to the magnitude of the rock dissolved by the selected acid recipe.
Filter cake removal using water-based and oil-based drilling fluids showed an effectiveness of 90% and 94.8%, respectively. Clear separation was observed between the oil sample and the acid recipe for the slightly gelled and fresh acid formulas. Calcium and magnesium concentration profile in flowback samples indicated the time when spent acid was recovered. Reduction in calcium concentration suggested calcium-based precipitation occurrence. The pH profile, in combination with density measurements, can assess the optimum shut-in and flowback time for full acid spending and retrieval. Steady pH profile at later times of the flowback revealed the presence of carbonic acid. The iron profile analysis was critical to determine the presence of corrosion products and the origin of iron ions in combination with chromium and manganese ions. Dilution factor of sodium and potassium ion concentration was used to determine water cut in acid flowback samples.
To develop scale management strategies and plans during field development planning, it is important to know the composition of formation water in the reservoir. Typically, formation water samples will be collected from appraisal wells and analysed for this purpose. However, when the wells are drilled with water-based mud, the samples are often contaminated with mud filtrate that has invaded the formation during drilling. By adding a tracer to the drilling mud and using a simple mass balance correction technique, it is possible to correct for the effects of contamination and obtain an estimate of the formation water composition. But, where reactions occur during invasion or within the sample after collection, this method of correction will generate an erroneous estimate of the composition. The errors will increase with the extent of reaction and degree of contamination.
In this paper, we describe a new ‘correction’ approach which additionally makes use of (a) 1-D reactive transport modelling of mud filtrate invasion and (b) modelling of reactions occurring in formation water samples after collection. This approach accounts for the potential effects of these reactions and provides an estimate of the formation water composition within uncertainty limits. It reduces the risk of obtaining erroneous estimates of formation water composition and is particularly beneficial where reactions occur and where the mud contamination fractions are elevated (e.g. ~10-40%). At higher fractions, the uncertainties can be so high that the estimated compositions are not useful, emphasising the risks of trying to estimate formation water compositions from heavily contaminated samples.
This approach has been applied to formation water samples obtained from the Nova Field (formerly Skarfjell, Norwegian North Sea). It has meant that the resulting composition and associated uncertainties have been used with more confidence in scale management planning; to select seawater as the injection water, and to identify the scale risks across the relevant nodes in the production process over the life of field of the asset. Based on these risks, appropriate scale mitigation and monitoring measures have been selected.
Numerous lost circulation materials (LCMs) are sold in the global market to cure losses in highly fractured formations, but the success rate remains minimal. Lost circulation (LC) is a common challenge of global operators and service companies during either drilling or the oilwell construction phase of development and exploration. A new chemical-sealant-based LCM (CS-LCM) was developed to cure severe-to-total losses in highly fractured formations. The new CS-LCM is dispersed in a nonaqueous carrier fluid (NAF) and quickly forms a highly malleable viscous mass upon exposure to an aqueous reactant fluid and then sets harder under a wide range of temperatures.
Comprehensive and systematic tests were conducted on the new CS-LCM to determine the speed of the reaction at an optimized interval of time upon interaction with the reactant. Testing performed on the new CS-LCM included evaluating its flowability before and after the reaction and estimating the compressive strength. Additionally, the developed strength robustness of the CS-LCM was evaluated by its ability to withstand large differential pressures across extra-large holes (31 mm) in test media (simulating vugs in a formation).
The reaction rate of the CS-LCM showed measurable right-angle viscosity (RAV) development once the CS-LCM was preconditioned at a bottomhole circulation temperature (BHCT) and allowed to mix with preconditioned (at BHCT) reactant. A significant amount of compressive strength (>500 psi) buildup was observed in less than 1 hour of reaction time, which sustained more than 1,000 psi differential pressure on large vugs. The fast increase in viscosity (i.e., RAV) and quick strength development are the result of fast-reacting chemical additives present in the mixture. Additionally, the resultant set CS-LCM was determined to be soluble in 15% hydrochloric (HCl) acid at ambient temperature; hence, it is a viable solution for a reservoir section.
The new CS-LCM was developed to mitigate severe-to-total losses in highly fractured formations by means of RAV development followed by rapid strength buildup in a short interval of time, thus helping prevent overdisplacement away from the wellbore, hence minimizing nonproductive time (NPT) and drilling mud losses.
Chendrika, Lusiana (Schlumberger) | Purwitaningtyas, I. M. (Schlumberger) | Fuad, Muhammad (Schlumberger) | Etuhoko, Michael (Husky-CNOOC Madura Limited) | Nurdin, Syaiful (Husky-CNOOC Madura Limited) | Jihong, Lian (Husky-CNOOC Madura Limited) | Rusli, Barne (Husky-CNOOC Madura Limited)
Manganese tetraoxide (Mn3O4) drilling fluid weighting material was first applied in two high-pressure/high-temperature (HP/HT) Madura Sea, Indonesia wells, BD-A and BD-B. Mn3O4 is less damaging to the environment and formation than other weighting agents. In the BD wells, coiled tubing (CT) will perform Mn3O4 mudcake removal by spotting an acid solution. The main challenges come from the formation characteristics: temperature up to 305°F, pressure of 8100 psi, 5,000 ppm H2S, and 5.5% CO2.
Slow-reacting acid was preferred to prevent creating a corrosive environment. The reaction of acetic acid, formic acid, and a chelating agent with Mn3O4 at 305°F was studied. A corrosion test was performed to see the effect of the acid and 5,000 ppm H2S on CT string and completion tubing metal. Viscosimeter and densitometer testing was done on 155 ppb Mn3O4 mud that was mixed at laboratory scale to represent actual drilling mud in the well. Filter cake was made using an HP/HT filter press and 10-micron alloxite disc to represent formation permeability.
Using the mix of acetic acid and chelating agent solution, 100% solubility of filter cake was achieved after 6 hours reaction time, giving enough time for CT to spot the acid in the entire 1,000-ft openhole interval and provide a uniform filter cake removal. With additional organic acid inhibitor and H2S inhibitor, the corrosion rate on CT and completion tubing metal after 16 hours test was found acceptable without pitting observed.
This method has been proven effective to remove Mn3O4 filter cake with significant pressure drawdown reduction, hence increasing well productivities. The utilization of CT improves cost efficiency by accurately placing a right amount of acid solution across the openhole section.
This stimulation fluid system is the first application in the world and was proven to be effective to remove Mn3O4 based filter cake and protect CT and tubing metal against H2S and CO2 in an HP/HT environment.
Liu, Yifei (China University of Petroleum) | Dai, Caili (China University of Petroleum) | You, Qing (China University of Geosciences) | Zou, Chenwei (China University of Petroleum) | Gao, Mingwei (China University of Petroleum) | Zhao, Mingwei (China University of Petroleum)
This article presents a novel organic-inorganic crosslinked polymer gel, which uses resin-silicate as the organic-inorganic crosslinker, to extend the temperature limitations of currently used polymer gels for water control in mature oilfields. The gelation performances, including gelation time, gel strength and thermal stability, were studied, and the optimum composition was selected by study of gelation performances. Results show that with increase of the concentrations of components, gelation time became shorter and gel strength was improved. And the gel system was stable after 90 days at 140 °C. The optimum composition of the gel system was selected as: 4~7 wt% resin and 2~5 wt% silicate with 0.1~0.3 wt% polymer. Meanwhile, differential scanning calorimetry (DSC) measurement was used to investigate the maximum tolerated temperature of the gel. The results showed that the chemical bonds of the gel began to break at 156 °C, which indicated that the gel can resist high temperature up to 156 °C. At last, environmental scanning electron microscopy (ESEM) microstructure and fourier transform infrared spectroscopy (FTIR) spectrum of the gel were studied to analyze the gelation process and investigate the mechanism for temperature resistance. The three-dimensional network microstructure of the resin-silicate crosslinked polymer gel was more compact and more uniform than the gel prepared without silicate. The formation of silicon-oxygen bonds (Si-O) increased the crosslinking density and temperature tolerance of the gel system.
A new laboratory work procedure has been developed to evaluate and test the performance and effectiveness of chemical-sealant-based loss circulation materials (CS-LCMs), which are often used in cases of severe-to-total losses. These unconventional testing methods should be useful tools to evaluate the integrity of loss circulation material (LCM) products under downhole conditions in terms of differential pressure buildup and how quickly such LCMs can arrest lost circulation.
Evaluation and testing of LCMs in the laboratory before field application are crucial. Conventionally, the plugging capacity of particulate LCMs is tested against various-sized slotted discs using a permeability plugging apparatus (PPA), and integrity is tested in terms of sealing capacity and fluid loss value. Testing the performance of CS-LCMs required another means that included plugging extra-large vugs and building a significant differential pressure that could sustain the drilling fluid column. Pumpability of CS-LCMs and mechanical strength performance over time were evaluated using a high-pressure/high-temperature (HP/HT) consistometer, ultrasonic cement analyzer (UCA), and modified PPA following this fit-for-purpose procedure.
Extensive laboratory testing revealed that the new testing method was highly compatible with almost all types of chemical-based LCMs, including resin, gunk squeeze, and thixotropic slurries. The effectiveness and performance of several commercially available CS-LCMs were measured using different vug sizes (i.e., up to tens of millimeters). Thickening time of LCMs were observed pumpable [i.e., <70 Bearden units of consistency (Bc)], even after hours of conditioning at bottomhole circulating temperatures (BHCTs). As per API routine practice, tested slurry is deemed unpumpable if Bc exceeds 70. However, the thickening time of gunk squeeze LCMs were observed to be significantly high in a short interval of time once aqueous and nonaqueous streams mixed together. Gunk-based LCMs build high differential pressures and compressive strength over the same periods of curing time at bottomhole static temperature (BHST) and pressure compared to thixotropic-based LCMs.
Appropriate laboratory testing and evaluation of chemical-based LCMs under downhole conditions are highly recommended before field trail/application. This new testing/evaluation method should help minimize operational risk and nonproductive time (NPT) at the rig site.
Effective zonal isolation is critical in lost circulation, cement repair and conformance applications. To be successful it is often necessary to not only block pathways but also ensure a tight seal. Gaps or weak points between the blocking material and boundary layers can result in poor zonal isolation leading to gas migration, gas entrapment, and/or excessive water production among other issues. The mechanisms vary but cement, polymers, and sodium silicate can all lose volume upon setting and aging. The degree of contraction being impacted by downhole events such as fluid loss, influx of gas, water or conditions such as high temperatures
In the case of Portland cement, several different methods have been developed to ensure dimensional stability. A long time approach has been the addition of aluminum powder to the cement slurry for the in-situ generation of hydrogen gas. This paper looks at how elemental aluminum as well as zinc can be adapted for use in a sodium silicate-based system. In developing a new technology, several questions are posed at the onset. At the top of this list are the health, safety, and environmental implications of the individual components and final product. Fine powders are inherently dusty and carry an explosive risk if not properly handled. Development of a safe form of the metal powders became the first priority. The direction taken was to slurry the metals using suitable base oils and mutual solvents. As part of the slurry development, the shape and size of the aluminum and zinc were studied for resistance to settling, rheological stability, and reaction kinetics.
Stable metal slurries could be formed in base oils such as polyalphaolefins or mineral oils when combined with other additives. The selected base oils were shown to function in a similar manner as encapsulators and be used control the rate of the gas generation reaction. Mutual solvents such as triacetin provided further functionality by being able to initiate a polymerization reaction of alkali silicate. Short-term properties such as set time, density, rheology, and compressive strength were made adjustable by concentration and the use of filler/bridging material such as walnut hulls, glass powder, calcium carbonate, barite, or fly ash.
While sodium silicates can be set by either an internal or external setting agent, the industry preference is for a one component system. Presented in this paper will be the development of a one component system that safely incorporates the in-situ generation of hydrogen to yield a chemically durable, mechanically strong expanded silicate-based plug.
Nedwed, Tim (ExxonMobil Upstream Research Company) | Kulkarni, Kaustubh (ExxonMobil Upstream Research Company) | Jain, Rachna (ExxonMobil Upstream Research Company) | Mitchell, Doug (ExxonMobil Upstream Research Company) | Meeks, Bill (ExxonMobil Development Company) | Allen, Daryl P. (Materia Inc.) | Edgecombe, Brian (Materia Inc.) | Christopher, J. Cruce (Materia Inc.)
Industry maintains well control through proper well design and appropriate controls and barriers. This has made loss of well control a very low probability event. Currently the final barrier to maintain control is a valve system (blowout preventer or BOP) located on top of wells capable of sealing around or shearing through obstructions that might be in the well (e.g. drilling pipe and casing) to isolate the well. Although the risk is low when proper drilling practices and design are employed, there are still concerns about well control especially for operations in sensitive environments. Adding an additional barrier could alleviate these concerns.
One scenario for well control loss is if the BOP fails to seal allowing drilling fluids and reservoir fluids to flow. We are currently evaluating a concept to respond to such an event and seal leaking BOPs by injecting a liquid monomer and a catalyst below a BOP leak point to form a polymer-plug seal.
Mixtures of dicyclopentadiene (DCPD) and other monomers mixed with a ruthenium-based catalyst cause a rapid polymerization reaction that forms a stable solid. These reactions can occur under extreme temperatures and pressures and withstand significant contamination from other fluids and solids.
Lab studies have shown that DCPD-based polymer plugs can withstand axial stress of 15,000 psi without significant deformation even at temperatures of 200°C and with 20% drilling fluid contamination. For well control, one option is to preposition monomer mixes and catalyst into pressurized cannisters located at or near subsea BOPs while drilling high-complexity wells. Connecting the pressurized cannisters to appropriate ports on the BOP will allow rapid transfer. During a well-control event, actuating valves would rapidly force the monomer mixes and catalyst from the cannisters into the BOP to initiate polymerization. Polymerization reactions can be as short as a few seconds depending on the monomer mix and catalyst. The resulting solid polymer plug will block the leak path to potentially seal the well.
This paper describes the concept details and summarizes the current status of research.
It is well known that refinery-petrochemical integration has the potential to optimize assets and sustain profits during oil demand cycles. For the same reason, it is also an important factor to reduce investment risk in new enterprises. Nevertheless, Brazilian oil refining facilities have never been effectively integrated to petrochemical units due to the chemical industry development model adopted in this country decades ago. However, there are still several integration opportunities that can lead to reduction of chemicals import, supply security and profitability increase.
This paper presents some interesting R&D initiatives related to refining-petrochemical integration, several of which are Brazilian particular issues an others with worldwide application.
Although some Brazilian refineries are able to produce MTBE using isobutylene from the FCC C4 cut, the majority of oil refining facilities in this country sell butenes as LPG. So, the use of butenes to produce chemicals rather than fuels has the potential to increase refineries profitability substantially. At Petrobras’ R&D centre, two projects are focusing on this subject: the use of butenes and fatty acids methyl esters to produce long chain linear olefins via metathesis, aiming the production of detergents, and the production of C12 olefinic compounds, from C4 oligomerization, for the formulation of synthetic-based drilling fluid, which can reduce/eliminate expensive chemical imports for Petrobras’ oil & gas production area.
Other refinery-petrochemical integration related projects, also being developed by Petrobras and university partnerships, aims propylene production and use, having a worldwide application character. An interesting initiative is the development of a propane/propylene facilitated transport membrane separation module, which can allow a substantial increase in the C3 splitter capacity. Also promising is the development of a high selectivity catalyst system to produce propylene from propane via oxidative dehydrogenation and the use of impure propylene to produce solvents.