Located in shallow water offshore Mexico, PEMEX’s AT Field is a naturally fractured heavy oil field that has historically been drilled with either total or partial mud losses, which creates a challenging environment for conventional wireline operations because of downhole restrictions in the highly deviated wells. These obstacles result in high failure rates for wireline log acquisition.
Of the 51 wells in the field, only 29% had wireline openhole logs, most of which were only partially completed because of issues caused by restrictions in reaching total depth. In 39% of the wells, only cased hole data was available, which helped provide porosity and saturation information but was limited in terms of natural fracture characterization. Additionally, 31% of the wells did not have any reservoir characterization information at all, limiting PEMEX’s capacity to make decisions that directly impact oil production in the field.
To collect data for a comprehensive reservoir characterization in this challenging environment, SLB recommended ThruBit™ through-the-bit logging services because of its proven formation evaluation performance in complex and unstable wells.
A suite of tools run on ThruBit service acquired data in the formation where it was previously impossible. ThruBit service tools provided a safer and more efficient way to capture high-resolution formation measurements. Data was collected using the following ThruBit service tools: telemetry, memory, and gamma ray; spectral gamma ray; neutron; density; induction; and acoustics. Additionally, ThruBit Dipole™ through-the-bit acoustic service provided data to create a discrete fracture network (DFN) model and the historical production adjustment. PEMEX plans to update this model using information from four additional wells where the same toolstring will be deployed. These combined technologies provided PEMEX with the data for subsurface characterization that was essential for critical decision making in such mechanically complex and highly deviated wells.
By integrating logging into the drilling plan, PEMEX saved more than 25% of operating time and related costs. ThruBit service enabled successful data acquisition from total depth to the casing shoe. By employing this high-quality data in 3D far-field sonic service, PEMEX generated a complete fracture characterization up to 30 m around the well, enabling PEMEX to better allocate production intervals and avoid early water production. Because of the insights provided from the comprehensive formation evaluation, PEMEX’s Well 48 well produces at a rate of 3,000 bbl/d without a water cut.
Building on the success of this first ThruBit service deployment for PEMEX in this field, the resistive borehole imaging tool was added to the toolset for a new well in this field, marking the first acquisition of ThruBit service resistive images at a national level in Mexico. This milestone has positioned the AT asset as a benchmark within PEMEX, inspiring other projects to adopt this innovative technology. The integration of borehole imaging data has been instrumental in advancing oil production from AT Field. By leveraging cutting-edge technologies and tools, these efforts have significantly reduced risks and boosted project profitability.
