Africa (Sub-Sahara) Bowleven has started drilling operations at the Moambe exploration well on the Bomono permit in Cameroon. Moambe is the second well in a two-well program, approximately 2 km east of the first well, Zingana. It targets a previously undrilled Paleocene Tertiary three-way dip fault block containing multiple sands and will be drilled to an estimated 1620 m in measured depth. Both wells will be logged. Bowleven is the operator and holds 100% interest. Asia Pacific Murphy Oil discovered gas at its Permai exploration well in deepwater Block H in the South China Sea offshore Malaysia. The find is Murphy's eighth consecutive success in the area around the Rotan floating liquefied natural gas project, which is planned to begin its first production in 2018.
Remya Ravindran Nair, Evgenia Protasova, Torleiv Bilstad, and Skule Strand, University of Stavanger Summary This research focuses on membrane-separation efficiencies by adjusting the ionic composition of deoiled produced water (PW) and evaluates the possibility for smartwater production from PW for enhanced oil recovery (EOR) in carbonate reservoirs. Key characteristics of smartwater for carbonate reservoirs are increased concentrations of divalent ions and low concentrations of monovalent ions compared with seawater. In this research, PW was pretreated with media filters, which resulted in 96 to 98% oil removal. This deoiled PW was used as feed for nanofiltration (NF) membranes. NF-membrane performance was evaluated in terms of flux and the separation efficiencies of the key scaling ions calcium (Ca) and barium (Ba). No membrane fouling was observed during the experiments. The results showed no Ca dissolution, which could affect chalk-reservoir compaction. A process scheme is proposed for smartwater production by ionic selection from seawater and PW at an operating pressure of 18 bar. Energy-consumption analysis for smartwater production before membrane treatment concluded NF to be economic over other desalination technologies. The power consumed by NF membranes for smartwater production at 18 bar is calculated at 0.88 kWh/m Introduction PW is one of the major waste streams from the oil and gas industry and should be managed in an environmentally sustainable manner. PW treatment is concerned with contaminants such as solids and residual oil, together with production chemicals (Fink 2012). The current water/oil ratio (WOR) in oil production is 2:1 to 3:1 worldwide. Onshore-treatment costs of PW from the North Sea differ from 0.19 to 3.40 USD/bbl of PW (Duhon 2012).
Imaging the geology subsalt and at the transition between extra-salt and subsalt has been a challenge at Mad Dog even with extensive seismic data coverage, including two WATS surveys and multiple NATS surveys. WATS acquisition and TTI velocity model processing generated major improvements in the image at Mad Dog. One of the observations of a previous TTI project is the presence of a strong orthorhombic anisotropic effect in a salt mini basin above the field. This finding led to the decision to reprocess the Mad Dog data with a tilted orthorhombic (TOR) velocity model. The main objective of this project is to build an orthorhombic velocity model with nine parameters compared to five with the TTI processing. The TOR anisotropic parameters are generated with the latest FWI and tomography techniques and take guidance from the stress field from a geomechanical model. The outcome of the project is very encouraging with results including better constructive imaging in crucial areas of the field, an incremental increase in signal-to-ratio everywhere and increased fault resolution. The TOR velocity model will be used to migrate a future ocean bottom nodes survey to address some of the remaining imaging challenges.
Presentation Date: Wednesday, October 17, 2018
Start Time: 8:30:00 AM
Location: 208A (Anaheim Convention Center)
Presentation Type: Oral
In the land known for the midnight sun, beautiful snow-clad mountains, and the green sky lights, there is a place where the "black gold" shines. The oil capital of Norway, the southwest coastal city of Stavanger has grown into one of the major international oil and gas hubs. As the importance of North Sea oil and gas production has increased for Europe, Stavanger has welcomed the world to its doorstep. The personality of Stavanger is not only oil and gas; in 2008, it was chosen as one of two European cultural capitals. A lively city, Stavanger embraces the diversity of the world's professionals who call Norway home.
Shale is a general term used for argillaceous (clay-rich) rocks which are the most abundant sediment on the earth. It is believed that clay rich rocks comprise more than 50-75% of the geologic column. Shale has very varying petrophysical and mechanical properties. Shale is in the most cases acting as a trap or seal for hydrocarbon migration, but has also in more recent years been targeted as a reservoir target in some basins. In some wells it has been observed on cement bond logs that shales in uncemented intervals have moved in and closed the annulus. Pressure communication testing has been performed on these sections and the sections has been qualified as well barrier elements (
In this paper we will discuss shale creep and other shale deformation mechanisms and how an understanding of these can be used to activate shale that has not contacted the casing yet to form a well barrier. We have developed a numerical model based on first order principles to better understand the mechanical deformation process. We are also supporting the modeling results with laboratory experiments, before we discuss a couple of field cases where shale intervals have been activated and verified to have formed a well barrier as part of the well construction process in new wells.
The last decade has spotted a tremendous upsurge in casing failures. The aftermaths of casing failure can include the possibility of blowouts, environmental pollution, injuries/fatalities, and loss of the entire well to name a few. The motivation behind this work is to present findings from a predictive analytics investigation of casing failure data using supervised and unsupervised data mining algorithms. Scientists and researchers have speculated the underlying causes but to date this type of work remains unpublished and unavailable in the public domain literature.
This study assembled comprehensive data from eighty land-based wells during drilling, fracturing, workover jobs, and production. Twenty wells suffered from casing failure while the remaining sixty offset wells were compiled from well reports, fracturing treatment data, drilling records, and recovered casing data. The failures were unsystemic but included fatigue failure, bending stresses from excessive dogleg, buckling, high hoop stress on connections, and split coupling. The failures were detected at various depths, both in cemented and uncemented hole sections. Failures were spotted at the upper and lower production casing.
Using a predictive analytics software from SAS, twenty-four to twenty-six variables were evaluated through the application of various data mining techniques on the failed casing data sets. The missing data was accounted for using multivariate normal imputation. The study outcome addressed common casing sizes and couplings involved with each failure, failure location, hydraulic fracturing stages, cement impairment, dogleg severity, thermal and tensile loads, production-induced shearing, and DLS. The predictive algorithms used in this study included Logistic Regression, Hierarchal Clustering, and Decision Trees. While the descriptive analytics manifested in visual representations included Scatterplot Matrix, and PivotTables. Failure causes were identified. A total of five statistical techniques using the aforementioned algorithms were developed to evaluate the concurrent effect of the interplay of these variables. Nineteen variables were believed to possess the highest contribution to failure. Scatterplot matrix suggested a complex correlation between the total base water used in fracturing simulation and casing thickness. Logistic Regression suggested nine variables were significant including: TVD, operator, frac start month, MD of most severe DL, heel TVD, hole size, BHT, total proppant mass, cumulative DLS in lateral and build sections variables as significant failure contributors. PivotTables showed that the rate of casing failure was highest during the winter season.
This investigation is aimed to develop a thorough understanding of casing failures and the myriad of contributing factors to develop comprehensive predictive models for future failure prediction via the application of data mining algorithms. These models intend to provide a theoretical and statistical basis for cost-effective, safe, and better drilling practices.
Sun, Zhuang (The University of Texas at Austin) | Tang, Hewei (Texas A&M University) | Espinoza, D. Nicolas (The University of Texas at Austin) | Balhoff, Matthew T. (The University of Texas at Austin) | Killough, John E. (Texas A&M University)
The reduction of pore pressure caused by depletion can induce significant reservoir compaction, especially in unconsolidated reservoirs. Experiments using unconsolidated core samples are often sparse and costly. We develop a numerical approach based on computer-based simulations of rock samples and mechanical tests. The numerical sample consists of crushable grains simulated with the discrete element method (DEM) and the bonded-particle model (BPM). Model parameters are calibrated through numerical single-grain-crushing tests which reproduce the experimentally-measured sand strength. Grain crushing induced by the uniaxial strain stress path results in a pronounced reduction of porosity and permeability, which manifests more readily for samples with large grain size. The change of particle size distribution indicates that the high effective stress causes grain crushing and produces a significant amount of fines. We perform numerical uniaxial strain tests on numerical samples comprising stiff and soft mineral grains. Simulation results indicate that the presence of soft grains and inclusions (e.g. shale fragments) facilitates the grain crushing. Reservoir simulations, incorporating the change of porosity and permeability as a compaction table, show that the upscaled compaction can enhance production due to compaction drive but also reduces production rate by impairing the reservoir permeability. This multiscale numerical workflow bridges particle-scale compaction behavior and field-scale reservoir production. In this paper, (a) DEM simulations provide a useful tool to investigate compaction effects and complement laboratory experiments; (b) the multi-scale numerical approach can predict the depletion-induced evolution of reservoir production.
Fluid injection into the subsurface perturbs the pore pressure and alters the effective stress quasi-statically, inducing seismicity on fractures of certain orientations (we hereinafter do not distinguish between a fracture and a fault in this study). This process is traditionally considered as a decoupled hydroshear process: the effective normal stress on a fracture simply decreases by the amount of fluid overpressure, whereas the shear stress remains unchanged (e.g., Byerlee, 1978; Scuderi & Collettini, 2016; Mukuhira et al, 2016), resulting in a direct increase in the Coulomb stress, which, when driven from negative to zero, signifies the occurrence of seismicity. Such a decoupled mechanism remains as the basis of some prevalent statistical models of induced seismicity in a permeable porous medium (e.g., Shapiro et al., 2005; Rothert & Shapiro, 2007). In this class of models, a statistically random critical pore pressure is used as a proxy of the frictional strength of a preexisting fracture and the pore pressure evolution is governed by simple linear fluid diffusion; the modeled spatialtemporal distribution of seismicity, however, is often inconsistent with observations. As a remedy, some nonlinear diffusion models have been developed by adding a pressure-dependent diffusivity (Hummel & Shapiro, 2012; Johann et al., 2016; Carcione et al., 2018). The diffusion-based seismicity models can be further extended by incorporating, e.g., random stress heterogeneity (Goertz-Allmann & Wiemer, 2012), fractures following distributions derived from field observations (Verdon et al., 2015), and even empirical seismic emission criteria for generating synthetic seismograms (Carcione et al., 2015). This decoupled mechanism also underlies some studies that invert for distributions of permeability (Tarrahi & Jafarpour, 2012) and pore pressure (Terakawa et al., 2012; Terakawa, 2014) from induced seismicity data. However, the decoupled mechanism inherently cannot explain the remoting triggering of seismicity in areas not subjected to pressure perturbation (Stark & Davis, 1996; Megies & Wassermann, 2014; Yeck et al., 2016); it also directly contradicts the commonly observed depletioninduced faulting (Zoback & Zinke, 2002).
Homburg, Janelle (ExxonMobil Upstream Research Company) | Crawford, Brian (ExxonMobil Upstream Research Company) | Fernandez-Ibanez, Fermin (ExxonMobil Upstream Research Company) | Freysteinson, Jordan (ExxonMobil Upstream Research Company) | Reese, William (ExxonMobil Upstream Research Company)
ABSTRACT: Natural fractures in fine grained carbonate reservoirs can modify reservoir behavior during hydrocarbon production because they increase both porosity and permeability of the host formation. These fractures, and their associated porosity and permeability, will respond to pore pressure changes associated with hydrocarbon production. The aim of this study is to evaluate this response using natural, partially cemented fractures. To this end a series of experiments was undertaken on fracture carbonate samples from Dry Canyon, NM. Fractures geometries were characterized via micro-CT imaging and petrographic analysis. Samples were then tested to determine their mechanical and hydraulic stress dependence. Results were fit with a semi-logarithmic closure model that relates fracture aperture change to applied stress and good agreement was found with the results of other studies. These findings support the use of this closure model in predicting the behavior of some naturally fractured carbonate reservoirs.
Produced water chemical compositional data are collected from a carbonate reservoir which had been flooded by North Seawater for more than 20 years, so there is an opportunity to analyse the large amount of produced water data collected, understand the brine/brine and brine/rock interactions and explore the impact factors behind them. In some publications, core flood experimental tests were performed with chalk cores or carbonate columns in order to make an understanding of possible chemical reactions occurring triggered by injected water with different composition (Seawater, low salinity water or any other brine). However, most of the time the laboratory conditions where core flooding experiments are implemented cannot fully simulate the real reservoir conditions. Therefore, in this study, with the help of the valuable produced water dataset and some basic reservoir properties, a one-dimensional reactive transport model is developed to identify what in situ reactions were taking place in the carbonate reservoir triggered by seawater injection.
From the perspective of reservoir mineralogy, calcite, as the dominant mineral in the carbonate reservoir, is relatively more chemically reactive than quartz and feldspar which are usually found in sandstone. Whether calcite is initially and dominantly present in the carbonate reservoir rock is dissolved under seawater flooding or not is the first key issue we focused on. The effects of calcite dissolution on the sulphate scaling reactions due to incompatible brine mixing and the potential occurrence of carbonate mineral precipitation induced by calcite dissolution are investigated and discussed in detail. The comparison of simulation results from the isothermal model and the non-isothermal model show the important role of temperature during geochemical processes. The partitioning of CO2 from the hydrocarbon phase into injected brine was considered through calculation of the composition of reacted seawater equilibrated with the CO2 gas phase with fixed partial pressure (equivalent with CO2 content), then subsequently the impact of CO2 interactions on the calcite, dolomite and huntite mineral reactions are studied and explained. We also use calculation results from the model to match the observed field data to demonstrate the possibility of ion exchange occurring in the chalk reservoir.