In 2009 Petroleum Development Oman LLC (PDO) started an ambitious tight and deep gas exploration programme exploring for previously untapped reservoirs. The exploration strategy is focusing on both conventional tight gas plays as well as deep unconventional gas resources. These resources are typically in previously undrilled formations at great depths, with high temperatures and unknown pressure regimes, and uncertain fluid fill and composition. The unique geological properties of this type of reservoir require different strategies and technology deployment in order to make them viable and sustainable.With unique Geomechanical, reservoir, and geological properties, some of the large gas-bearing prospects within the Fahud Basin in the Sultanate of Oman require innovative drilling and completion practices. A revised drilling and completion workflow, with specific technology deployment and operational flexibility, has been developed in order to account for such reservoir complexity. This workflow includes the incorporation of rock strength acquisition and stress state of the reservoir prior to completion, in order to identify targets for hydraulic fracturing and quantify hydraulic fracturing performance versus reservoir deliverability. The unparalled challenges encountered whilst exploring for these resources required resolving to new technologies from outside the region and adapting them to local conditions (Briner et al, 2012). This paper demonstrates how the understanding of the Geomechanical stress regime obtained through the integration of data from multiple Petroleum Engineering disciplines helped to determine the location & orientation for the first horizontal well in a new Tight Gas discovery. In addition the paper will summarize the results of a Geomechanical analysis that aided the planning of appropriate hydraulic system to maintain borehole integrity in the Build-Up and Horizontal sections of the well through the highly stressed overburden and reservoir sections.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMeasurement of continuous permeability profiles on a routine basis has become possible through recent advances in wireline logging hardware and software. Continuous permeability profiles allow geologists, and reservoir engineers to better characterize their reservoirs and to more efficiently complete and manage the production of the hydrocarbon reserves. One of the most promising methods for the calculation of continuous permeability information is the use of Stoneley wave data acquired using a monopole acoustic device. This paper presents the results of a case study conducted for Petroleum Development Oman (PDO) in which permeability is determined from Stoneley wave data for two wells, namely Sarmad-1H2 (SAR-1H2) and Sarmad-2H1 (SAR-2H1), penetrating the carbonate reservoirs of the Ara group in Oman. The objectives of the study are:1. To demonstrate the validity of the methodology. 2. To test whether this method can be used on a routine basis aimed at obtaining a continuous permeability index for completion evaluation purposes.The Stoneley wave derived permeability profile is compared with permeability data from other sources, such as, core data, wireline pressure tests, and interpretation of nuclear magnetic resonance measurements.The results of this case study clearly demonstrate the great potential of using Stoneley wave for permeability prediction.
In-situ reservoir stress measurements are essential input to a wide variety of the production and injection applications of reservoirs. Most of the reservoirs in this article require water injection to maximize recovery without breaking the matrices unintentionally. In some cases, it is also important to create a controlled fracture growth in a formation unit without breaking bordering barriers or zones. The main purpose of the in-situ reservoir stress testing of the case studies in this article is to calculate the minimum stress to improve the reservoir management plans for well placement, production, injection and fracturing processes.One approach of measuring stresses in many zones is to use the wireline conveyed stress testing tools. The wireline conveyed in-situ reservoir stress testing measurements are frequently performed in the Sultanate of Oman for a wide range of operational and geomechanics applications such as but not limited to:• Hydraulic fracturing • Fracture growth/containment issues • Polymer injection • Borehole stability • Sand production prediction • Stress evolution with depletion, hot and cold injectionThe stress testing zones vary from tight to high permeable zones as well as shale zones. The complexity and wide variety of the stress testing applications inevitably led modifications and improvements on the wireline conveyed stress testing tools. These improvements mainly are various types of pumps, higher performance dual packers and mandrels, innovative stress testing methods. The latest improvements and methods in stress testing help addressing the broader range of formations (deep and shallow, tight and permeable) in an extensive type of wells from vertical or deviated to horizontal.In this article, the examples of several unique stress testing applications are presented. Shale stress testing with a viscous fluid, horizontal well stress testing, tight and very high permeability formation stress testing, sleeve fracturing stress testing methods are discussed in details.
Measurement of continuous permeability profiles on a routine basis has become possible through recent advances in wireline logging hardware and software. Continuous permeability profiles allow geologists and reservoir engineers to better characterize their reservoirs and to more efficiently complete and manage the production of the hydrocarbon reserves. One of the most promising methods for the calculation of continuous permeability information is the use of Stoneley wave data acquired using a monopole acoustic device. This paper presents the results of a case study conducted for Petroleum Development Oman. In this study, permeability was determined from Stoneley wave data from the Sarmad-1H2 and Sarmad-2H1 wells that penetrated the carbonate reservoirs of the Ara Group of Oman. The Stoneley-wave derived profile was compared with permeability data from other sources; such as, cores, wireline pressure tests, and the interpretation of nuclear magnetic resonance measurements. The results demonstrated the validity of the methodology and showed that Stoneley-wave data can be used on a routine basis to obtain a continuous permeability indication for completion evaluation purposes. The method has great potential in permeability prediction.
This paper discusses the Geomechanical interaction between vertically stacked reservoirs, two of which are currently producing and deeper reservoirs that are being considered for development. The shallowest Natih reservoir is a highly compacting carbonate gas reservoir under depletion whereas the intermediate Shuaiba reservoir is an oil-bearing reservoir under water flood. The deeper reservoirs are oil and gas bearing located in the Sudair and Khuff formations. Interpretation of 3D seismic data shows a major NE/SW and NW/SE fault system separately developed in all reservoirs. Depletion in the shallow gas reservoir (Natih) has induced a subsidence bowl and has caused a subset of the faults (NE/SW) to reactivate causing seismic tremors that are often felt at surface. Water injection in the oil-bearing reservoir (Shuaiba) is believed to cause some additional localized micro seismic activity around the NE/SW fault system (5 to 10% of observations). Consideration is being given to developing the deeper (Sudair and Khuff) reservoirs under natural depletion. A geomechanics assessment study has been initiated to assess whether such a development would significantly add to the geomechanics related risks and if so how these risks could be mitigated. This paper presents data inputs, workflow, calibration, results and preliminary conclusions related to the geomechanics assessment study. The impact of depletion and injection on fault reactivation and subsidence bowl of all reservoir layers are investigated using the in-house proprietary finite element modeling software tool. An extensive dataset [logs, laboratory tests, field measurements, well and reservoir monitoring data (compaction monitoring instrument, microseismic) as well as surface deformation data (GPS and InSar)] is utilized to constrain and derive the stress state as well as the rock mechanical properties of each reservoir layer and the various overburden layers. Introduction Given the exisiting observations of subsidence and localized fault reactivation, the study focuses on: 1. Safety and environment: · Effects of Sudair and Khuff depletion on the currently reactivating faults: magnitude and frequency of tremors and potential gas leakage2. Well and reservoir management (WRM) and urban planning of the new development faciltities · Assess additional compaction damage to the existing wells, especially given that recent surface deformation surveillance tools (GPS and InSar) reported a noticeable acceleration in the measured subsidence· Decide on new well placement and trajectory relative to the seismic tremor belt and appropriate casing design· Decide on facility placement relative to the seismic tremor belt and the subsidence bowl A previous geomechanical study [1] has focused on understanding and predicting future compaction/subsidence caused by the Natih reservoir. The incentive was to to assess what damage this compaction could have on the 450+ (Natih and Shuaiba) wells drilled through this compacting reservoir. The current study includes deeper reservoirs in the modeling, assesses the effect of depletion on fault reactivation and uses non-linear computations for all scenarios investigated. A typical geomechanic workflow consists of three components (Tripod approach): Laboratory data,Field data andModeling efforts.
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