Abstract
In recent years, great efforts have been focused on tight oil reservoirs in Ordos Basin, which is located in North Central China. Although historical field development in these tight oil reservoirs was still economical, average production after hydraulic fracturing is quite low and most of wells produce just at the margins. In order to understand production potential through appropriate completion and fracturing techniques, a pilot project was initiated recently on two horizontal wells drilled in parallel, with three vertical wells placed between two horizontal wells along the lateral for real time fracturing monitoring.
This paper describes how the treatment design was optimized based on detailed formation evaluation and fracture simulation using a 3D unconventional fracturing design workflow. It presents real time fracture mapping results through a dual monitoring well setup on total 26 stages of fracturing treatments, and also illustrates how the results were utilized to adjust and optimize treatment design during and between treatment stages. The paper demonstrates the application of a unique Unconventional Fracture Model (UFM) that was developed for design and evaluation hydraulic fracturing treatment in unconventional reservoirs. The model incorporates predefined natural fracture patterns and interaction criteria for hydraulic and natural fractures. The paper also discusses the outcome of simultaneous treatments tested in four stages compared to other stages pumped in sequences.
Initial production tests on both wells show 124.5 m3/d and 103.2 m3/d respectively, which are significantly higher than all the wells completed in tight oil reservoirs in the basin, of which the production varies from 5-8 m3/d in vertical wells to 32 m3/d in horizontal wells on average. In-depth reservoir understanding, advanced design and evaluation workflow, and appropriate completion and fracturing technique are the key of this success, which has set a milestone for developing such tight oil reservoirs in Ordos Basin.
