Propellant-Assisted Perforating in High-Pressure and Temperature Wells at Campo Bosque in Northern Monagas State

Abstract

Abstract The Pirital Field is located in the eastern basin of Venezuela and is characterized by large high-pressure/high-temperature (HP/HT) reservoirs. The geology is complex with heavy faulting, natural fracturing and high-formation dip angles. To optimize the evaluation of the new HP/HT reservoirs in the Bosque block, a development and delineation project team was assembled. To fully assess the potential of the HP/HT reservoirs, two exploratory wells were drilled (PIC-25 and PIC-26) to confirm the feasibility of drilling and completing these wells. The mission of the project team was to deliver prolific producers with optimum completion efficiency while minimizing environmental impact. One of the most important tasks was the perforation planning to ensure adequate connectivity to the reservoir in order to successfully test and evaluate each respective horizon. Available petrophysical data indicated that the reservoirs under study were of low porosity (<5%) and permeability (<0.8 md) at a measured depth of 21,000 ft. Several perforating strategies were evaluated, and the final decision was to use propellant-assisted perforating in scenarios where conventional hydraulic fracturing was not in the evaluation plans. This paper covers the methodology used to validate the application of propellant-assisted perforating in HP/HT wells. The perforation-gun assembly selection, along with the analysis of generated peak pressures from the propellant burn process, will be reviewed. The mechanical configuration, wire line design and benefits derived from propellants will be fully explained. The results presented in the two case histories presented will show the benefits observed in the form of low completion skin factors. Propellant-assisted perforating has shown to be an effective method for achieving perforation breakdown when testing tight, HP/HT sandstone reservoirs. Introduction The Pirital Field is located in eastern Venezuela, 75 km from Maturin, capitol of Monagas State, in the North Monagas area (as shown in Figure 1). One of the most prolific producing areas in the country, the field is approximately 46 square miles. Presently, the field is in the development stage with seven wells producing an average of 14,000 BOPD and 10,000 Mscf\D. The wells drilled in the area are vertical or slightly deviated and the oil is produced from various formations located between 20,574 and 20,532 ft; 20,265 and 20,574 ft; 19,698 and 20,265 ft; and identified as the Naricual Inferior, Medio, and Superior formations. Two deep exploratory HP/HT wells (PIC-25 and PIC-26) were drilled in the North Monagas area by PDVSA to evaluate the potential of the deeper Cretaceous formation. Following the drilling phase, the zones of interest were cased off with a 5 1/2-in. liner and the well was completed as a 5 1/2-in. monobore completion. The wells were temporarily abandoned and the rig moved off location pending the testing operation. The Pirital formation petrophysical data (shown in Table 1) indicated that these particular zones were considered as tight, hard rock. The challenge in completing these two exploratory wells was to source a perforator with a shaped-charge performance that would penetrate past any near wellbore damage and restore connectivity to the natural fracture system. Therefore, perforation techniques for this HP/HT environment were evaluated to determine optimum performance in this naturally fractured hard rock.