Improving drilling hydraulics estimations ‑ a case study

Accurate pressure drop estimation is important for drill string and bit nozzles design and optimized fluid circulations as well as identifying the drilling problems such as bit nozzle(s) washout or plugging. In this study, the Bingham Plastic model has been modified by applying a coefficient to its turbulent pressure loss calculations. This coefficient encompasses the effects of the drill pipe tool joints and other effects in estimation of pressure losses. The range of the coefficient was determined in field applications for different hole sizes and mud types. The results showed that applying a correction coefficient of 1.08–1.12 to turbulent pressure loss equations (depending on borehole size and mud type) improves the pressure loss estimation. By applying this coefficient, the estimated pressure losses are increased to compensate the under-estimation of the Bingham Plastic model. This is considered a significant contribution to accurate calculation of borehole hydraulics and in-time detection and identification of borehole problems and reduction of invisible lost time. The findings also showed that this enhanced effect is independent of the mud type. The use of this coefficient removes the necessity of using rather complex mud rheological models such as the Herschel–Bulkley model.publishedVersio

Production Improvement via Optimization of Hydraulic Acid Fracturing Design Parameters in a Tight Carbonate Reservoir

Hydraulic fracturing can be utilized to extract trapped hydrocarbon where integrated fracture networks do not exist for sufficient production. In this work, design parameters of a hydraulic acid fracturing of a tight carbonate reservoir in the Middle East were optimized. The effect of optimized hydraulic fracturing on production performance and rate was investigated. Using the petrophysical well logs, formation integrity tests, core data the Mechanical Earth Model (MEM) of the tight carbonate reservoir was created, which resulted in rock mechanical properties and in-situ stresses. The other required parameters for fracturing design were either measured or found from empirical correlations. Following a candidate selection of suitable layers for fracturing, the input parameters were loaded in GOHFER software to design and optimize the fracturing job. Finally, the production forecast was performed and compared with current conditions. The injection parameters (flow rate, total volume, and number of stages) of the fracturing fluid (composed of guar and CMHPG and polymer with 15% HCL acid) were optimized to reach optimum resultant fracture geometry. Finally, optimized injection parameters were found at the injection flow rate of 18 barrels per minute, total injection volume of 90 K-gal, and three stages of injection. Using the optimal injection parameters, the optimized fracture geometrical sizes were determined: the fracture half-length (Lf): 148 m (486 ft), fracture height (Hf) of 64 m (210 ft) and fracture width (Wf) of 0.0962 in. Finally, the effect of this stimulation method on future production performance was investigated. The well production rate showed an increase from 840 STB/Day (before fracturing) to 1270 STB/Day (post fracturing). This study contributes to the practical design and optimization of hydraulic fracturing in the tight carbonate formation of the investigated oilfield and the other potential fields in the region. The results showed that this stimulation method can efficiently improve production performance from reservoir formation

Production Improvement via Optimization of Hydraulic Acid Fracturing Design Parameters in a Tight Carbonate Reservoir

Hydraulic fracturing can be utilized to extract trapped hydrocarbon where integrated fracture networks do not exist for sufficient production. In this work, design parameters of a hydraulic acid fracturing of a tight carbonate reservoir in the Middle East were optimized. The effect of optimized hydraulic fracturing on production performance and rate was investigated. Using the petrophysical well logs, formation integrity tests, core data the Mechanical Earth Model (MEM) of the tight carbonate reservoir was created, which resulted in rock mechanical properties and in-situ stresses. The other required parameters for fracturing design were either measured or found from empirical correlations. Following a candidate selection of suitable layers for fracturing, the input parameters were loaded in GOHFER software to design and optimize the fracturing job. Finally, the production forecast was performed and compared with current conditions. The injection parameters (flow rate, total volume, and number of stages) of the fracturing fluid (composed of guar and CMHPG and polymer with 15% HCL acid) were optimized to reach optimum resultant fracture geometry. Finally, optimized injection parameters were found at the injection flow rate of 18 barrels per minute, total injection volume of 90 K-gal, and three stages of injection. Using the optimal injection parameters, the optimized fracture geometrical sizes were determined: the fracture half-length (Lf): 148 m (486 ft), fracture height (Hf) of 64 m (210 ft) and fracture width (Wf) of 0.0962 in. Finally, the effect of this stimulation method on future production performance was investigated. The well production rate showed an increase from 840 STB/Day (before fracturing) to 1270 STB/Day (post fracturing). This study contributes to the practical design and optimization of hydraulic fracturing in the tight carbonate formation of the investigated oilfield and the other potential fields in the region. The results showed that this stimulation method can efficiently improve production performance from reservoir formation

Statistical analysis of past kicks and blowouts occurred in a Middle Eastern oilfield

Abstract In 2017, blowouts and then explosions occurred in a Middle Eastern oilfield. A root cause of the incident is lack of study and investigation of the past kicks and blowouts data. Therefore, as a pioneer work in the region, data gathering and analysis of past kicks and blowouts were made in the studied oilfield to learn lessons and find gaps. Out of the 149 drilled wells, a total of 117 kicks and three (3) blowouts occurred. In this work, a list of drilling parameters to be considered in data gathering and analysis were suggested as a guideline for future works elsewhere. The statistical analysis not only showed all the three exploration wells kicked which is not a surprise, but it also showed that 39 out of 146 (26.71%) also experienced kicks during reservoir drilling. The large number of kicks in development wells proved that possibility of kick occurrence in development wells is not low. In exploration wells, the predominant kick causes were gas-cut mud and insufficient mud weight which indicates the necessity of using pressure while drilling in addition to drilling rate control systems in exploration wells. However, in development wells, lost circulation was the predominant kick cause indicating the necessity of using low-weight drilling fluids and managed pressure drilling systems. The direct role of human error exists at least in 60% of kicks occurred in this field, which shows the great importance of improved drilling personnel training. Although only 3.45% kicks in development wells occurred due to improper hole fill-up during tripping, this cause should not only be deemed trivial, but it should also be taken seriously as being the cause of the blowout. The 2.56% possibility of kick conversion to blowouts and 67% risk of blowout conversion to explosion emphasize the necessity of maintaining primary well control and using efficient and early kick detection systems. Bullhead was the more commonly used method than standard well control methods; as this kill method may not always be safe, its application should be revised

Cellulose nanocrystals (CNCs) as a potential additive for improving API class G cement performance: An experimental study

Integral cement sheaths are crucial for safe and economical hydrocarbon production throughout the well lifecycle. Cement additives tailor short- and long-term cement properties for various well conditions to ensure well integrity. Although various additives exist, the current trend in reducing the carbon footprint motivates the developing ''greener” additives that are environmentally friendly and made from renewable and sustainable sources such as cellulose nanocrystals (CNC). CNCs exhibit superior properties and have shown significant impact on cement slurry, including increased degree of hydration, strength, and altered properties. However, most studies on CNCs are intended for construction industry rather than hydrocarbon and geothermal well cementing. Investigating the use of CNCs as high-performance cement additives is therefore of interest due to their potential benefits. This study aims to determine the effect of CNC on vital well cement properties. The effects of CNC were determined using standard American Petroleum Institute (API) test procedures and equipment in an experimental approach. The experimental findings indicate that the addition of cellulose nanocrystals (CNC) at a concentration of 2 vol% resulted in a notable increase of 7% in viscosity, a significant decrease of 50% in free water, a remarkable reduction of 78% in cement shrinkage, and no discernible effect on slurry thickening time. Furthermore, the inclusion of a 0.2 vol% of CNC yielded a significant surge of 56% in compressive strength after 21 days and accelerated 500 psi strength development by 9%. However, the investigation revealed that a concentration of 1.5 vol% of CNC represents a threshold concentration or the turning point, beyond which the addition of CNC can negatively impact the studied cement properties

An Experimental Investigation of Drilling Performance Improvement Using Reaming While Drilling

International audienceAbstract This work investigates the drilling performance by reaming while drilling (RWD) using a dual-body bit and compared it with conventional drilling by a standard drilling bit. The dual-body bit consisted of a 2.45-in. pilot bit located at a short distance ahead of a 2.47 × 3.97-in. reamer. Conducting a series of drilling experiments at a simulation drilling rig with full monitoring sensors, we further studied the drilling performance as a function of the distance between the pilot bit and the reamer. This distance is a greatly important parameter affecting mud diffusion and the resultant change in pore pressure and stress. A method was devised to eliminate the drill-string vibration and its effect on the drilling performance and the energy consumed. The mechanical-specific energy (MSE) calculated for each case was considered as a drilling performance indicator. Using two laboratory experiments as well as analytical thermo-poro-elastic calculations of the Mechanical Specific Energy (MSE), the MSE changes were monitored and recorded. Comparison of this drilling performance indicator was used in both the RWD and the conventional drilling assembly to analyze the effect of RWD. Based on the results, with increasing the distance between the pilot bit and reamer, there is an increase in improvement of drilling performance in terms of MSE reduction. The best drilling performance indicator (MSE reduction of 84%) was observed with the greatest distance between the pilot bit and the reamer of 43.3 cm. The best drilling performance indicator (MSE reduction of 84%) was observed with the distance between the pilot bit and the reamer of 43.3 cm. This is considered a novel finding in reaming while drilling

Improving drilling hydraulics estimations ‑ a case study

Accurate pressure drop estimation is important for drill string and bit nozzles design and optimized fluid circulations as well as identifying the drilling problems such as bit nozzle(s) washout or plugging. In this study, the Bingham Plastic model has been modified by applying a coefficient to its turbulent pressure loss calculations. This coefficient encompasses the effects of the drill pipe tool joints and other effects in estimation of pressure losses. The range of the coefficient was determined in field applications for different hole sizes and mud types. The results showed that applying a correction coefficient of 1.08–1.12 to turbulent pressure loss equations (depending on borehole size and mud type) improves the pressure loss estimation. By applying this coefficient, the estimated pressure losses are increased to compensate the under-estimation of the Bingham Plastic model. This is considered a significant contribution to accurate calculation of borehole hydraulics and in-time detection and identification of borehole problems and reduction of invisible lost time. The findings also showed that this enhanced effect is independent of the mud type. The use of this coefficient removes the necessity of using rather complex mud rheological models such as the Herschel–Bulkley model