Optimization of Hydraulic Horsepower to Predict the Rate of Penetration

The rate of penetration has an important role in the success of a drilling operation, this is because if the rate of penetration is not optimum will have an impact on the cost incurred. Some factors that influence the rate of penetration are the weight on bit, rotation per minute and horsepower. Based on the analysis obtained WOB and RPM values are optimum so that optimization is done on horsepower. In this case study the well that will be analyzed is vertical well so that bit’s hydraulic optimization is performed using Bit Hydraulic Horse Power (BHHP) method by adjusting the nozzle size and circulation rate, this method will be optimum if BHHP / HPs ratio is 65%. Evaluation on trajectory 12 1⁄4 well “SGT-01” field “Tranusa", obtained bit’s hydraulics on the actual conditions at 2657.48 ft 2723.10 ft depth interval obtained Bit Hydraulic Horse Power (BHHP) of 232.67 hp, Horse Power Surface (HPs) 499.82 hp, Horse Power per Square Inches (HSI) of 1.67 hp / in2 and percentage (BHHP / HPs) of 46.55% (<65%) indicating less optimum then optimized hydraulic bit circulation rate optimized to 710 gpm with Horsepower Hydraulic Horse Power (HPH) of 936.47 hp, Horse Power per Square Inches (HSI) of 5.4 hp / in2 and percentage (BHHP / HPs) of 65% (already optimum). The final result of the evaluation and optimization of bit hydraulics and the removal of cutting is predicted to increase ROP from 46 fph to 125.66 fph.


Introduction
Increasing the complexity of drilling operations has increased some of the issues that make drilling cost considerations [1]. There are several parameters that affect drilling performance and if not done properly or optimum, the company will lose money because it does not save the cost of drilling exactly adds to the cost issued. Some of these parameters, among others, weight on bit (WOB), rotation per minute (RPM), flow rate, bit hydraulics and bit type are the most important drilling parameters affecting the rate of penetration (ROP) and the drilling economy. The rate of penetration is directly proportional to drilling parameters such as WOB, RPM, and Horsepower making it a very important methodology in considering the previous drilling data and making optimum drill prediction [2].
It has long been known that drilling fluid properties can dramatically impact drilling rate. This fact was established early in the drilling literature, and confirmed by numerous laboratory studies. Several early studies focused directly on mud properties, clearly demonstrating the effect of kinematic viscosity at bit conditions on drilling rate. In laboratory conditions, penetration rates can be affected by as much as a factor of three by aitering fluid viscosity. It can be concluded from the early literature that drilling rate is not directly dependent on the type or amount of solids in the fluid, but on the impact of those solid on fluid properties, particularly on the viscosity of the fluid as it flows through bit nozzles. This conclusion indicates that drilling rates should be directly correlative to fluid properties which reflect the viscosity of the fluid at bit shear rate conditions, such as the plastic viscosity. Secondary fluid properties reflecting solids content in the fluid should also provide a means of correlating to rate of penetration, as the solids will impact the viscosity of the fluid [3].
The factors which affect rate of penetration are exceedingly numerous and perhaps important variables exist which are unrecognized up to this time. A rigorous analysis of drilling rate is complicated by difficulty of completely isolating the variable under study. For example, interpretation of field data may involve uncertainties due to the possibility of undetected changes in rock properties. Studies of drilling fluid effects are always plagued by difficulty of preparing two muds having all properties identical except one which is under observation. While it is generally desirable to increase penetration rate, such gains must not be made at the expense of overcompensating, detrimental effects. The fastest on-bottom drilling rate does not necessarily result in the lowest cost per foot of drilled hole. Other factors such as accelerated bit wear, equipment failure, etc., may raise cost [4]. Optimization of drilling hydraulics can be obtained by increasing the drilling rate [5].
In this paper, Hydraulic horsepower has an important role in drilling operations, the timing of drilling also greatly affects the costs incurred. The size of the horsepower is directly proportional to the rate of penetration (ROP) where the greater the horsepower the faster the rate of penetration. Basically, the parameters associated with the rate of penetration in the drilling hydraulics include weight on bits, rotation per minute and horsepower. Optimization of hydraulics needs to be done to obtain optimum drilling results if the rapid penetration rate will be obtained a good drill cleaning effect, good cutting removal, no regrinding and no bit balling.

Method
The steps were taken in hydraulic optimization and cutting removal are as follows: 1. Calculating actual bit hydraulics. 2. Calculating the actual lifting of the cutting hydraulics. 3. Calculate the maximum pressure conditions. 4. Calculating Qmin. 5. Calculating Qmax. 6. Bit hydraulics optimization. 7. Optimization of hydraulic removal of cutting.

Drilling Hydraulic and Cutting Lifting Optimization
Data processing performed on drilling hydraulics includes calculation of pressure loss on the bit, percentage of pressure loss on the bit and loss of surface power. Calculation of Pressure Loss on Flow System Except on Bit (Pp) is done by calculating the average velocity of mud and critical velocity in both the circuit and in the annulus.

Calculation of Pressure Loss on Flow System Except on Bit
Loss of pressure on the flow system except on the bit is influenced by the flow patterns occurring within ranges and annulus, the first step to determine the flow pattern by calculating the average velocity of the mud and the critical velocity of the mud, if V> Vc then the flow pattern is turbulent otherwise V <Vc then the flow pattern is laminar (Rabia, H., 1985).

Calculation of Average Flow Rate of Mud (V)
The average velocity of mud flow (V) using the equation: After determining the flow patterns that occur in the string and in the next annulus calculate the loss of pressure on the surface connection (PSC). Total loss of pressure on the system is usually expressed in the equivalent of the discharge line consisting of 4 categories, including flow line, stand pipe, swivel, and Kelly. Based on the type of surface connection used in the drilling operation can be seen the price of constant pressure loss pressure on the surface. As shown in Table 1 and Table 2 below. The amount of pressure loss on the surface connection is calculated by the equation: The flow is Laminar, then it is calculated by using the equation: Where: PV = Plastic viscosity, cp. ID = Inner Diameter, inch. L = Length, ft. YP = Yield point, 100lb/ft. The flow is Turbulent, then it is calculated by using the equation:    (Rabia, 2002) After calculating the loss of pressure then calculates the total pressure loss (parasitic pressure loss) on the flow system by using the equation: Pp = Psc + PDP + PDC + PHWDP + PMWD + PanDP + PanDC + PanHWDP + PanMWD

Calculation of Actual Hydraulics Bit Using BHHP Method
The basic principle of this method assumes that the greater the power delivered by the fluid to the rock will be the greater the cleaning effect so that the method seeks to optimize the horsepower used on the surface of the pump. The BHHP concept assumes that hydraulic optimization is achieved when the lost horsepower on the bit is 65% of its power. The BHHP concept is suitable for drilling on vertical wells and rock types with consideration of gravity (Rabia, H., 1985).
Where: Q = Rate, gpm Pb = Pressure Loss on bit, psi Calculation of how much power on the bit used to clean the bottom of the wellbore during drilling activity, namely by comparing BHHP price with the large power pump on the surface (HPs) (Rabia, H., 1985).
Determining the Horse Power Per Square Inch (HSI) value:  Figure 2 shows the curve relationship between horsepower and rate of penetration. In low horsepower conditions, the cleaning effect of small holes and small ROP. ROP price increase can be known by increasing horsepower. But at some point, the sharp increase in speed is achieved from the relatively small speed (Carl Gatlin, 1960).

Calculation of Actual Cutting Hydraulics
Based on the physical properties of the drilling mud used, the power law index is calculated by the equation: Where: K = Indeks konsistensi. n = Indeks power law. ρ = Density, ppg. OD = Outer Diameter, inch. DH = Hole Diameter, inch. The apparent viscosity is calculated using the equation: Where: DH = Hole Diameter, inch. OD = Outer Diameter, inch. Va = mud Velocity, fps. Vsa = direct mud Velocity, fps

Calculating Qmax Pump
Calculation of the maximum pump flow rate of the combined three pumps, namely the duplex pumps arranged in parallel as follows: Calculate maximum pump power (HPmax):

HPmax = HP pump max × Eff pump × Number of Pumps
Calculates maximum pump flow rate (Qmax):

Qmax = Number of Pumps × Qmax pump × Eff pump
Calculate pump maximum pressure (Pmax) using the equation: XY(

Qmin with the Annular Velocity Minimum Concept
The calculation of Qmin using the Minimum Annular Velocity method begins with determining the velocity slip cutting (Herianto and Subiatmono, 2001). Velocity slip is the minimum velocity where cutting can begin to rise or in practice is a reduction in velocity mud and velocity falling from the cutting expressed by the equation:    The calculation result of mud flow average in Wells "SGT-01" in the example of Depth Interval 2657.48 ft -2723.10 ft (trajectory 12 ¼ ") can be seen in Table 3. Because VanDP <VcanDP then the flow is laminar The calculation result of mud flow average in Wells "SGT-01" in the example of Depth Interval 2657.48 ft -2723.10 ft (12 ¼ " trajectory) can be seen in Table 4. -The value of f is obtained from Figure 1 is for DP of 0.003197 -PDP Calculation with Equation (7

Calculation of Actual Hydraulics Using BHHP Method
The percentage of pressure loss on the bit compared with the pump pressure on the surface can be known after knowing the magnitude of parasitic pressure loss (Pp).
Calculation of pressure loss on the bit (PB)

Calculation of Actual Cutting Hydraulics
The calculation steps used to optimize the removal of cutting by drilling mud using the CuttingTransport Ratio (Ft) method, Cutting Concentration (Ca) and Particle Bed Index (PBI) are exemplified in the calculation with Depth Interval 2657.48 ft -2723.10 ft (trajectory 12 ¼ " ) are as follows: Based on the physical properties of drilling mud used, the power law index is calculated by Equation (12) Consistency Index is calculated by using Equation (13) 510.ρ dh dp 3n The results of the actual drilling powder lift calculations exemplified at the 2657.48 ft -2723.10 ft (12 ¼ " trajectory) depth can be seen in Table 5.  Table 6.  Based on the evaluation of% BHHP / HPs, ROP and BHHP at the depth of 909.55 ft-2723.10 ft shown in Table 6 found the price of% BHHP / Hps less optimum, where% BHHP / HPs condition is still below 65% aims to raise the price of% BHHP / HPs. BHHP value is closely related to ROP value, where if BHHP value is small then ROP is also small otherwise if BHHP is big value then ROP is also big value, it is illustrated in (Figure 3). Basically one of the purposes of this research is to raise the ROP, if the ROP is high then the target drilling time can be achieved well. The results of Minimum Annular Velocity calculations at the "SGT-01" Wells at the 2657.48 ft -2723.10 ft (12 × 12 cm) Depth Interval can be seen in Table 7.

Hydraulic Bit Optimization
Optimization is done by trial and error by raising the Rate parameter and pump pressure, but in trial and error also must pay attention to the efficiency of each pump's ability to be used optimally. On bit hydraulic optimization and removal of "SGT-01" wells with a depth interval of 2657.48 ft-2723.10 ft. Pumps are arranged in parallel. Results of trial and error optimization of bit hydraulic well "SGT-01" can be seen in Table 8. After BHHP optimization, it is possible to predict the increase of ROP by extrapolation, the result of the predicted increase of ROP after BHHP optimization. The predicted increase of ROP can be illustrated in (Figure 4) where the trendline in actual condition and optimization shows the change of ROP value after BHHP is optimized.
Extrapolation of ROP vs BHHP is obtained from the trendline on the graph, that is: y = 0.2149X-5.1672 y = (0.2149 x 650) -5.1672 y = 134.51 fph Basically, in conducting an evaluation of mud hydraulics and removal of cutting, WOB and RPM parameters are also related to BHHP, but in this paper, the authors focus on the evaluation and optimization of hydrolysis that is by predicting the increase of ROP because in this case study WOB and RPM parameters considered optimum.
At (Figure 4) it can be concluded that the predicted increase of ROP is obtained by extrapolating linearly, so that ROP value will be reached up to the optimum condition that is 65% BHHP / HPs, where after passing the restriction then ROP will decrease so that regrinding occurs (reforestation) and bit bailing.

Optimization of Cutting Apparel
Furthermore done trial and error optimization of cutting appointment, in optimizing cutting appointment, there are some parameters that influence to reach the optimum result.
Some of the parameters that influence the optimization of cutting appointment are Rate (Q), pump pressure (P) and rate of penetration (ROP). Results of trial and error optimization of cutting wells "SGT-01" can be seen in Table 9.