Assessment of Lost Circulation Material Particle-Size Distribution on Fracture Sealing: A Numerical Study

Summary Lost circulation materials (LCMs) are essential to combat fluid loss while drilling and may put the whole operation at risk if a proper LCM design is not used. The focus of this research is understanding the function of LCMs in sealing fractures to reduce fluid loss. One important consideration in the success of fracture sealing is the particle-size distribution (PSD) of LCMs. Various studies have suggested different guidelines for obtaining the best size distribution of LCMs for effective fracture sealing based on limited laboratory experiments or field observations. Hence, there is a need for sophisticated numerical methods to improve the LCM design by providing some predictive capabilities. In this study, computational fluid dynamics (CFD) and discrete element methods (DEM) numerical simulations are coupled to investigate the influence of PSD of granular LCMs on fracture sealing. Dimensionless variables were introduced to compare cases with different PSDs. We validated the CFD-DEM model in reproducing specific laboratory observations of fracture-sealing experiments within the model boundary parameters. Our simulations suggested that a bimodally distributed blend would be the most effective design in comparison to other PSDs tested here.

Modified Corn Starch as an Environmentally Friendly Rheology Enhancer and Fluid Loss Reducer for Water-Based Drilling Mud

Summary Drilling fluid rheology and fluid loss property are fundamental parameters that dictate the effectiveness and easiness of a drilling operation. Maintaining these parameters under high temperatures is technically challenging and has been an exciting research area for the drilling industry. Nonetheless, the use of drilling mud additives, particularly synthetic polymers, threaten ecological environments. Herein, modified corn starch (MCS) was synthesized, characterized, and investigated as an environmentally friendly rheology enhancer and filtration loss controlling agent for water-based mud (WBM) at high temperatures. The experimental results indicated that MCS exhibits better performance in improving rheological properties and fluid loss controlling ability for WBM than the commonly used mud additives. With the addition of an optimal concentration (0.3 wt%), MCS improved the rheology and fluid loss behavior of WBM formulation at harsh aging temperature (220°C) by practically 4 times and 1.7 times, respectively. The MCS was revealed to perform superbly over polyanionic cellulose (PAC) addition at all investigated temperatures. The better performance of the MCS was ascribed to the improved entanglements in the mud system owing to the additional hydroxyl (OH) groups. Besides, the Herschel-Bulkley model was found to be a constitutive model that described the rheological properties of the investigated muds satisfactorily. Moreover, the MCS was found to exhibit acceptable biodegradability properties.

Nanomagnetit-bentonit vizes közegű diszperz rendszereinek zeta-potenciáljának vizsgálata

The stability of different type nanomaterials play an important role among recent scientific and industrial challenges, including the examination of the effect of polymers, surfactants and their mixture on surface and electric surface properties and aggregation extent of dispersed particles, which are of utmost importance. Bentonite and its composite with different nanomaterials are frequently used for instance in environmental protection for wastewater treatment, since due to their great specific surface area they have excellent sorption properties. There are several publications in the literature for the application of bentonite in drilling muds. By using them the fluid loss can be decreased during the drilling process, the filtration of the fluid can be increased, it also improves the rheological properties and the formation damage can also be mitigated. During research the investigation and the analysis of the zeta-potential of nanoparticles and their composites at different pH and salt content can be an interesting topic. During our experiments the electric surface properties of nanomagnetite synthetized in laboratory (NM), cation exchanged bentonite from Mád (Be) and the composite particles of these particles were investigated. Hybrid particles of different compositions (9:1, 7:3, 1:1, 3:7, 1:9) were analyzed at different potassium chloride concentrations (0.1 – 0.0001 M). The surface adsorption on the surface, i.e. the change in the surface charge can be traced well by analyzing the obtained zeta-potential values. The behavior of such systems was observed in the full pH interval, thus, valuable data were obtained regarding the colloidal stability. As for the stability, different requirements may emerge in practice, there are application fields where the colloidally stable system is advantageous, on the other hand, in some cases, ceasing the stabile system is the goal. Our investigations are of high importance in terms of stability and its characterization [1].

Research of Bare-Free Drilling Fluids

Mining and geological conditions for the development of new fields are becoming more difficult every year. Accordingly, the requirements for ensuring the environmental and technological safety of the drilling process are becoming more and more important. To ensure such a process, it is necessary to use correctly selected drilling fluids with proper characteristics: rheological parameters sufficient for effective cleaning of the well bottom, density sufficient to create back pressure, fluid loss to ensure a high-quality filter cake. Modern environmental requirements dictate the abandonment of hydrocarbon-based solutions. But when using water-based solutions, there are no suitable solutions, especially with their high density, since the use of barite can lead to a decrease in reservoir productivity. In this regard, the analysis of the problem and the search for options for creating water-based drilling fluids, weighted without the addition of barite, having the properties of maintaining the stability of the wellbore, ensuring safe drilling and opening productive formations without damaging the reservoir characteristics, was carried out. Such a solution was found in changing the base of the drilling fluid - highly mineralized fluids or solutions based on saturated brines. Brines must be created on the basis of inorganic salts that have good solubility, for example, chlorides, bromides. Due to the content of salts, the fluids have an inhibitory effect, and depending on the volume of dissolution, the density of the drilling fluids can be controlled. The scientific works of foreign and domestic scientists analyzed in the article have been published over the past five years, which indicates the relevance of this development. The selected compositions are presented and theoretically investigated, which were also tested in the field conditions.

Simulation of Pressure- and Temperature-Dependent Fracturing Fluid Loss in Multi-Porosity Multi-Permeability Formations

In this paper, the multi-porosity multi-permeability porothermoelastic theory is used to derive the analytical solution to calculate the pressure- and temperature-dependent fracturing fluid loss. A triple-porosity triple-permeability source rock formation is selected as an example to illustrate the model. The effects of fracturing fluid temperature and natural fractures on the fluid loss rate are systematically illustrated. The model successfully accounts for the varying leak-off rates in the multi-permeability channels through the hydraulic fracture faces. Furthermore, thermal diffusion near the hydraulic fracture faces contributes to a variation of pore pressure whose gradient at hydraulic fracture faces directly controls the fracturing fluid leak-off rate. The model shows that thermal effects bring almost 27% variation in the leak-off rate. Comparison study indicates that the single porosity model without considering multi-permeability systems or thermal effects significantly underestimates the rate of fracturing fluid loss and predicts nearly 84% and 87% lower leak-off rate, compared to the dual-porosity dual-permeability and triple-porosity triple-permeability models, respectively. Two case studies using published laboratory measurements on naturally fractured Blue Ohio sandstone samples are conducted to show the performances of the model. It is shown that the model presented in this paper well captures the total leak-off volume during the pressure-dependent fluid loss measured from laboratory tests. Matching the analytical solution to the laboratory data also allows rocks’ double permeabilities to be estimated.

Application of a Novel Ecofriendly Okra Powder as Fluid Loss Controller in Water Based Drilling Fluids

Saudi Arabian based companies are spending many millions of dollars a year on import of drilling mud additives to meet the drilling industry demand. To cut the imported materials, locally available materials are preferable. Out of many drilling fluid additives, a single locally available additive such as fluid loss can save millions of dollars a year. The cost and locally available raw material justify the development of drilling fluid additives in the Kingdom of Saudi Arabia. In other aspect, local development provides many benefits to the Kingdom including industrial growth, technology ownership and new job opportunities. Okra (Hibiscus esculents) is widely used as a thickener and viscosifier in medical and food industries due to its low cost, availability, longer shelf life, and high thermal tolerance. In addition to that, it is environment friendly and available in abundance locally in Kingdom of Saudi Arabia. The composition of Okra powder was diagnosed by X-ray fluorescence (XRF) and Fourier-transform infrared spectroscopy (FTIR). The thermal stability of Okra was tested using thermal gravimetric analysis (TGA). The Okra powder was mixed in various concentrations such as (1, 2 and 3) grams in 350ml of water based drilling fluid (WBDF). The performance of Okra contained drilling fluids was compared with starch-based drilling fluid. The addition of Okra reduced fluid loss in different proportions at different concentrations. For instance, drilling fluid with 3g Okra concentration had 42% lower fluid loss as compared to the base fluid. The cake thickness was reduced upon the addition of Okra. The low fluid loss and thin filter cake make Okra a useful solution as a fluid loss controller in WBDFs. The addition of Okra powder also increased the viscosity and gel strength of the WBDFs. TGA analysis of Okra powder showed that it has strong thermal stability as compared to starch. Overall, the experimental results suggest that Okra mixed drilling fluids can be used as an alternate solution to starch mixed drilling fluids.

LAPAROSCOPIC SANTULLI INTESTINAL ANASTOMOSIS IN AN INFANT WITH CYSTIC FIBROSIS

The aim of the study was to evaluate the technical feasibility of performing a Santulli-type side-toend inter-intestinal anastomosis in infants with cystic fibrosis (CF) using laparoscopy. A clinical case of a 3-month-old child with CF who was operated on in the neonatal period for meconium ileus is presented. The baby's gestational age was 32 weeks. The primary operation consisted of the formation of a terminal enterostomy. In the postoperative period, a malabsorption syndrome was noted, accompanied by a lack of growth. As a temporary measure to restore nutritional status, a Santulli-style side-to-end laparoscopic intestinal anastomosis was performed. The observed child was found to have the F508del mutation in both alleles of the CFTR gene. The patient's weight at the time of the Santulli anastomosis construction was 2900 g, the age – 3 months. During the operation, there were no difficulties associated with the mobilization of the separated segments of the ileum. The duration of the surgical intervention was 70 min. Enteral nutrition was started on the 3rd day after the operation. The recovery period for intestinal transit through the rectum was 15 days. The postoperative period was uneventful. The duration of hospitalization was 18 days. No electrolyte imbalance or excessive fluid loss or underweight associated with enterostomy was observed. Over the next 6 months, the normalization of age-related weight and height parameters was achieved, after which the continuity of the digestive tract was restored by closing the terminal enterostomy. Currently, the patient has minimal respiratory symptoms and is receiving adequate CF therapy with pancreatic enzyme replacement therapy included with each meal. The initial experience of performing laparoscopic Santulli inter-intestinal anastomosis in an infant with CF presented in the study showed the possibility and reproducibility of this technique, expanding the boundaries of laparoscopy in pediatric practice. The decision to close the enterostomy in these patients should be deferred until a full diet is introduced and should be made in conjunction with a pediatrician specializing in the treatment of CF.

PENGARUH JUS KULIT BUAH SEMANGKA (Citrullus lanatus) TERHADAP STATUS HIDRASI ATLET DI UKM SEPAK BOLA

Background: Football as a high-intensity sport that causes fluid loss in the body often makes athletes dehydrated which results in decreased athlete performance. Provision of adequate and appropriate drinks can prevent dehydration. Watermelon rind contains high potassium which can restore lost body fluids.Objectives: Conducted a study to determine the correlation of giving watermelon rind juice to the hydration status of athletes in the Student Football Activity Unit.Methods: The study was conducted with a quasi-experimental design with a pre-posttest without control group design. A sample of 18 soccer athletes was taken using a purposive sampling technique. Subjects were given 300 ml of watermelon rind juice for 7 days. Hydration status was obtained based on the results of urine specific gravity examination. Measurement of hydration status wasconductedbefore and after the intervention period. The research instruments were urine samples analyzed in the laboratory, SOPs for making watermelon rind juice, observation sheets for giving juice, SOPs for measuring hydration status, and hydration status observation sheets. Data analysis using Wilcoxon test.Results: Specific gravity of pretest urine obtained a median of 1.025 g/dl (min-max 1.005-1.030 g/dl). Posttest urine specific gravity received a median of 1.025 g/dl (min-max 1.010-1.031 g/dl). There was an average decrease in urine specific gravity of 0.0019 g/dl at the posttest. The results of the pretest and posttest bivariate analysis obtained a p-value of 0.391.Conclusion: There is no significant effect of watermelon rind juice on the hydration status of athletes in the Student Football Activity Unit. There is a decrease in the average specific gravity of urine after being given watermelon rind juice

Research and Application of Micro-Expansion and Anti-Channeling Cement Slurry System in Agadem Oilfield

The overall liner cementing qualification rate is only 40% in Agadem block of Niger, The cement slurry system used in the field has a UCA transition time of 43min, and an expansion rate of -0.03% in 24h, which result in a poor anti-gas channeling performance. The expansive agent and the anti-gas channeling toughening agent of anti-channeling agent were optimized through experiment study. A novel micro-expansion anti-gas channel cement slurry system which is suitable for Agadem block was obtained through experiment optimization study: 100% G +2 ∼ 4% fluid loss agent +3 ∼ 4.5% anti-channeling agent +1 ∼ 2% expansion agent-100S +0.15 ∼ 0.4% retarder +0 ∼ 0.3% dispersant +0 ∼ 0.25% defoamer + water. This new cement system has a good anti-gas channeling performance, the cement strength is 24.5-35.0MPa after 24hrs, the UCA transition time is 16-18min, and the expansion rate is 1.5-1.7%. At the same time, a cementing prepad fluid suitable for the block and the micro-expansion cement slurry system is selected to ensure the performance of the cement slurry's anti-channeling performance. The field test results proofs the good performance of the new cement system. The cementing qualification rate of Koulele W-5 well is 96%, and the second interface cementation is Good. The cementing qualification rate of Trakes CN-1 well is 100% which second interface cementation is Excellent. This paper has positive guidance and reference for cementing in Agadem block.

Cement Evaluation in Highly Laminated and Multi-Stacked Sandstone Reservoirs: The World First Novel Approach Using Dual-Physics Cement Bond Assessment

Advances in cement recipe, additives and cementing technology including light weight cement, ultra-low fluid loss cement blend and improved cement to mud rheology mixing to seal the continuous liquid channels have prompted the industry to find an innovative way to evaluate the cement bond and integrity with a more robust and integrated approach. Evaluating cement bond behind casing based on single tool platform had shown some inherent uncertainties mainly due to borehole effects, tool eccentralization and processing variation. This paper will highlight few case studies on the application of both electromagnetic acoustic wave (EMAT) and ultrasonic cement evaluation logs including the world's first tool combination in single run to enhance understanding on cement integrity and optimize the perforation interval for production. Channeling and microannulus occurrences whether dry or wet are the most common features in cement integrity evaluation and yet poorly characterized to prevent any unwanted cross-flow or adverse impact to production. Electromagnetic acoustic wave cement evaluation in combination with an ultrasonic tool allow direct quantification of compressional, shear and flexural attenuation properties of cement downhole as well as acoustic impedance and microdebonding feature of the cement. Separation between average shear and flexural attenuation curves may indicate presence of microannulus depending on the extent of the separation without any requirement of additional pressurized logging pass. Parameter threshold determination based on shear and flexural attenuation cross-plot also indicates severity of cement microdebonding. Results showed that good production rate with lower water cut and low GOR reading had been achieved from specific perforated zones in the well. Electromagnetic acoustic wave and ultrasonic cement evaluation tools had successfully defined the zonal isolation layers as thin as 2 to 3 meters along the wellbore and optimized the perforated zones to avoid any liquid channeling or premature water and gas breakthrough into the wells, which can affect the production attainability and drainage efficiency from particular reservoirs. In a nutshell, combination of EMAT acoustic wave and ultrasonic cement evaluation principles prove to provide a more comprehensive overview on the cement bond integrity behind the casing. Having two independent downhole measurement which complement each other will reinvent the effort in cement bond assessment for complex reservoir environment which is susceptible to interpretation ambiguity.