Numerical Modeling of Multiple Hydraulically Fractured Horizontal Wells (MHFHW)

Abstract

Horizontal wells with multiple fractures are becoming more prevalent in the Industry. They are especially beneficial in carbonate plays where acid and fracture stimulation can be used to improve productivity, the technique can be used for tight reservoirs and multiple compartments or anisotropic reservoirs with high permeability contrasts. Reliable evaluations of stimulation performance are required for field development planning. As such, pressure transients are often used, and can be successful, tight reservoirs where transient flow regimes can be used to observe and define the various impacting factors of stimulation, such as fracture length, conductivity, orientation, etc. This project investigates the modeling and interpretation of pressure transient responses of multiple hydraulic fractured horizontal wells (MHFHW) using a numerical reservoir model. After validating the numerical model using an analytical solution applied to a simpler reservoir/well model, complex reservoirs are simulated and pressure transient response signatures obtained. Sensitivities of key reservoir/well/fracture properties are investigated and a result of each case is presented. Finally, an actual case where seven transversal fractures of a long horizontal well is modeled using a sector of the full field reservoir simulation model (geological/structural), where the results are interpreted and discussed. Fracture characteristics have been approximately estimated by comparing real well test pressure buildup analysis from field and simulation results. Introduction The field studied is a carbonate formation in the Jurassic horizon in Saudi Arabia. It has been on development since 1945. Two predominant layers exist in this formation, C and D. The study herein is limited to the different zones comprising of layer D. Carbonate reservoirs are inherently heterogeneous in nature, in part due to the environments in which they are deposited and their subsequent diagenetic alteration. Layer D in this region is characterized by contrasts in rock properties. Variations in lithology, limestone and dolomite zones, porosity and permeability contrast of two orders of magnitude are common in this region. A typical formation D stratigraphic column consists of seven zones. Zone 1 at the top of the reservoir; contains the more developed porosity and permeability, is the most prolific and does not typically require stimulation. In contrast, zones 2 and 3 are classified as tight reservoir, thereby restricting hydrocarbon production when commingled at existing drawdown conditions with other more productive layers. Zones 4 and 5 exhibit better rock quality than 2 and 3, but they still benefit from stimulation. The bottom zones - 6 and 7 - similar to zone 2 and 3 in being tight, are best completed with selective fracture stimulation treatments. A well in this reservoir was selected to be acid stimulated using a multi-stage open hole completion system with isolation, mechanical diversion and selective fracture ports allowing the fractures to be placed at specific positions along the wellbore (Al-Naimi et al., 2008). Offset oil producers in the vicinity of this well demonstrate relatively high levels of total well production, but recent production logging results confirmed that contribution is dominated by dolomite section (zone 1). The result of this can lead to inefficient reservoir sweep and reduced or deferred recovery.

Evaluation of Multi-Fractured Horizontal Well Performance: Babbage Field Case Study

“…Eventually, pseudoradial flow will develop when flow across tips of the horizontal well becomes dominant (Soleimani, Lee, Ghuwaidi, & Dyer, 2009). Well test analysis was performed on the vertical appraisal well and all the three horizontal wells.…”

Fracture Parameters Optimization of BZ Oilfield Horizontal Well Integral Fracturing

“…Injection and production exploitation of horizontal well can substantially raise productivity of single well and the whole exploitation benefit of the block. Integral fracturing of horizontal well technology is the forefront of low permeability reservoir development [5][6][7][8][9], the reseach of integral fracturing of horizontal well technology was still in its infancy at home and abroad.Therefore, aiming at injection and production of horizontal wells fracturing for BZ oilfield, theoretical model of fracture parameters optimization of horizontal well overall fracturing is established, fracture parameters of horizontal well fracturing of the specific well pattern is obtained.…”