A Better Well and Better Fracturing Improve Production in B-Field, Offshore Northwest Java
Authors: Vico Hendro , Arieffiandhany Riezal , Sanjaya Indra , Francisco Lambertus , Setiawati Yasinta Dewi , Afimanya Aldifa Rizqi , Syuhada Prawoto , Pramadana Aditya Bintang , Madyanova Mutiara , Purwoko Tunggal , Makmun Areiyando 
Published: October 2021

B-Field is located in Northwest Java and holds potential hydrocarbon in its low-quality marine sandstone reservoir, BR-34A and BR-34B zones. Each zone has a permeability range between 5 and 12 mD and can only produce approximately 20 to 50 BFPD without stimulation, making the well a non-economic producer. In 2020, two infill development wells, A-08 and K-08, were drilled targeting these zones. Both wells were planned to be completed with hydraulic fracturing stimulation to boost the production.

The first well, A-08 was completed earlier than K-08, but the production result from the well was unsatisfactory. The pressure evaluation analysis indicated high near-wellbore pressure of more than 1,000 psi. There were no reliable mechanical properties data in the well, which led to a conservative final hydraulic fracture design to avoid fracture growth into the nearby watered-out zone, BR-35. Therefore, only 30,000 lbm of proppant were pumped, resulting in minimal proppant concentration in the pay interval for this reservoir of 360 lbm/ft even though the optimum amount of proppant for this type of reservoir is 1,000 lbm/ft. Limited proppant ramping concentration of only 6 PPA was also affecting proppant width around the wellbore, especially in this low Young's modulus reservoir. Because of this conservative design approach, the minimum target parameter from conductivity, dimensionless fracture conductivity, proppant concentration, does not meet optimum fracture half-length and skin. Eventually, the well could only produce 100 BFPD.

A first application in the field of a comprehensive study of geomechanics using a sonic dipole log was performed to create a 1D mechanical earth model (MEM) on the second well, K-08, to validate the risk of breaking into the nearby water zone. In addition, this study was critical to confirm static rock properties and to revise the stress profile considering reservoir pressure change. As a result, it confirmed that the zones have enough competent shale barrier to hold the proppant volume according to the recommended design and that the zone has low Young's modulus (0.4 to 0.7 million psi) as well as lower stress compared to the preliminary estimation. A new technical approach then considered these additional facts to determine that a smaller proppant size with a larger amount of proppant would be optimal for maintaining width integrity and reducing the embedment effect.

By using pressure evaluation software on the second well, better permeability and with less near-wellbore friction pressure were achieved. Later, a pressure match simulation analysis with optimum pad volume, larger volume of proppant, and higher proppant concentration resulted in a contained fracture in the zone of interest that did not break through the barrier into the watered-out BR-35 zone. Hence, the second well (K-08) has improved production performance with the well able to deliver over 500 BFPD.