Analyzing Production Data From Tight-Oil Wells

Abstract

Performance prediction of wells producing from tight microdarcy formations is a daunting task. Complexities of geology (the presence/absence of naturally occurring fractures and contribution from different lithological layers), completion and fracture geometry complexities (multiple transverse and/or longitudinal fractures in long horizontal boreholes), and two-phase flow are impediments to simple performance forecasting. We demonstrate the use of various analytical and numerical tools to learn about both short- and long-term reservoir behaviors. These tools include (a) traditional decline-curve analysis (Arps formulation), (b) Valko's stretched-exponential method, (c) Ilk et al's power-law exponential method, (d) rate-transient and transient-PI analyses to ascertain the stimulated- reservoir volume, and (e) numerical simulation studies to gain insights into observed flow regimes. The benefits of collective use of analytical modeling tools in history-matching and forecasting both short- and long-term production performance of tight-oil reservoirs are demonstrated with the use of real and simulated data. Diagnosing natural fractures, quantifying stimulated-reservoir volume, and assessing reliability of future performance predictions, all became feasible by using an ensemble of analytical tools.

Moving boundary approach to forecast tight oil production

“…Calculations of EUR also vary with the selection of fitted curves, a problem that only is alleviated by fitting more production data. Various methods such as Arp's, PLE, SE, RTA, and transient PI methods were compared in estimating oil‐in‐place in fractured tight formation 13 . The dynamic material balance was developed in estimating original‐gas‐in‐place when the production rate is variable 14 .…”

Formation conditions and distribution patterns of N1 tight oil in Zhahaquan Area, Qaidam Basin, China

“…Tight oil refers to oil accumulation which didn’t migrate for a long distance in the source rocks or the reservoir rocks like the tight sandstone and the tight carbonate in the forms of absorbing or unbound state, and the tight sandstone is found interbedded with the source rocks (Jia et al., 2012). Foreign countries have done a great deal of research work on tight oil reservoirs and have successfully developed multiple tight oil and gas reservoirs such as the Bakken, the Eagle Ford, and the Barnet (Kabir et al., 2010). In recent years, explorations show that there are tight oil reservoirs with huge resource potential in the upper Ganchaigou formation (N 1 ) of the Zhahaquan Area of the Qaidam Basin.…”

Study on Extended Reach Horizontal Well Multistage Fracturing Techniques for Tight Oil

“…Tight oil reservoirs have low porosity, low permeability, low production and high development costs, which requires a lot of horizontal well drilling and multi-stage fracturing to achieve commercial development value [1,3]. Generally, horizontal wells are applied in unconventional tight oil formation with horizontal length range from 1000m from 1500m [4,6]. In order to increase the reserves controlled by single well, slow down production decline and enhance economic efficiency, extended reach horizontal wells multi-stage fracturing with average 40 stages and 2954m horizontal length were studied and successfully applied in Cardium tight oil formation, Daylight oil field, which have a great significance to the development of tight oil formations in other fields.…”