Hydraulic Fractures Monitoring using Microseismic Techniques in Clastic Reservoir - A Pilot Test Case from India

Abstract

Clastic gas reservoirs can be made economical through effective stimulation techniques. Hydraulic fracture mapping based on seismic techniques can lead to better understanding of the effectiveness of reservoir stimulation, when combined with in-depth reservoir geology and geophysical knowledge make development of such fields feasible. Two stages, out of five hydraulic fractures stimulation were monitored and mapped in an attempt to assess the fracture propagation in a clastic gas reservoir located in Rajasthan, Western India. This was the first hydraulic fracture monitoring in India using downhole wireline sensors whereby recorded microseismic (MS) events indicating fracture growth as they are being created by rock failure. Events triggered by the stimulation treatment are detected and located in a four-dimensional (4D) space (space and time) relative to the well being treated. The microseismic images indicate that fractures are well distributed within the Upper and Lower Fatehgarh formations, in the north-east south-west azimuth. The first monitoring was done on Stage-4 and recorded very few MS events, but indicated a relatively contained fracture. The fracture geometry estimated from the mapping matches closely with the parameters anticipated from the frac modeling work. The second monitoring was done on shallower Stage-5 and showed downward height growth during the initial stage of the treatment. This observation indicates that the hydraulic fractures may have intercepted a fault located within the treatment well. The result is being integrated with the planned stimulation model, mini-frac data, stress profile and other geological information. This will help in calibration of the stimulation model. Understanding of the fracture geometry from this technique along with the fracture geometry available from fracture modeling, well testing, etc. shall be combined to arrive at optimized designs for future fracturing campaigns in this clastic gas reservoir.

Refracturing Strategy for Sevensprings Oilfield in China Based on Geological and Engineering Characteristics

“…We analyze the failure reasons of initial fracturing in Sevensprings. The reasons could be divided into four types according to the data from previous fracturing and historical production (Al-Garni et al, 2005;Lim et al, 2011;Rahman et al, 2007).…”

“…Identified the principle stress was around 30MPa and 25MPa. At last, the artificial fracture azimuth was determined by fracture detection data for different well groups (Lim et al, 2011). Based on the data we obtained, Combined with the characteristic of the target well group, we build the feature model which considered formation properties.…”