Research and Development Petroleum Conference and Exhibition 2018

In this contribution, a robust theoretical approach was applied to predict the interfacial and phase equilibrium properties of real reservoir fluids. The modeling approach was based on an improved version of the Peng-Robinson equation of state (EoS) and on the Density Gradient Theory (DGT) for fluid interfaces. All the EoS and DGT parameters were obtained from literature correlations or calculated through a group-contribution method, leading to the computation of all the fluid properties in a fully predictive manner. The good agreement with volumetric, phase composition and interfacial tension data of multiple contact tests confirmed the superior predictive capabilities of the present modeling approach for describing key PVT properties of reservoir fluids.

Most of Middle East fields presents harsh reservoir conditions (high temperature, high salinity, low permeability carbonates) for polymers used as mobility control agents in EOR. Traditional synthetic polymers such as partially hydrolyzed polyacrylamide (HPAM) are not thermally stable. At temperatures higher than 60°C, acrylamide moieties hydrolyze rapidly in sodium acrylate which ultimately leads to precipitation and a total loss of viscosifying power. Thermal stability can be improved by incorporating more expensive monomers such as ATBS or NVP.

In a previous paper (Tulsa, 2014), we reported the development of terpolymers where the incorporation of NVP brought robustness up to 120°C. However, the use of NVP increased the cost of the polymer and limited its molecular weight. NVP also caused compositional drifts impairing injectivity in low permeability carbonate rocks. The price of the final product was 3 times higher than conventional HPAM polymers and 2 to 2.5 higher than SPAM polymers. In a more recent paper (ADIPEC, 2017), we reported the synthesis of NVP-free polymers having different contents of ATBS. These polymers presented had a lower cost than the NVP polymers and allowed a dosage reduction of 50% to get the same viscosity. They outperformed the NVP polymers in terms of injectivity and thermal stability pushing further the envelope of stability of EOR polymers up to 130°C and 140°C in brines having a TDS of 230 g/L and 100 g/L respectively.

In this study, we present new data of viscosity and thermal stability of the NVP-free polymers optimized in terms of process and molecular weight. In particular, the thermal stability study was completed with NMR spectroscopy and Size Exclusion Chromatography (SEC) analysis to bring information on the evolution of the chemistry and of the molecular weight distribution of the polymers under aging. Results showed that the optimization of these polymers allowed an additional dosage reduction of 30% compared to NVP polymers. NMR and SEC analysis revealed that the reduction of the viscosity during aging was due to an evolution of the chemistry by the formation of sodium acrylate but also to chain scission. ATBS appeared to slow-down hydrolysis and limit viscosity loss. No modification of the chemistry was observed for the polymer having the highest level of ATBS. Its viscosity loss was directly correlated to a decrease of its molecular weight.

The optimization of the NVP-free polymers allowed reducing their dosage by one third making them very attractive from an economic perspective. NMR and SEC have proven to be an efficient tool to better understand the evolution of the viscosity of the polymer solutions submitted to aging.

In this paper, we investigate a fractured reservoir zone in an oilfield located in the Emirate of Abu Dhabi, United Arab Emirates, by using seismic wave attenuation attribute.

The dense geometry of a 3D VSP walkaway spiral survey carried out in the oilfield, permits to perform a high resolution (15° spacing) azimuthal estimation of the attenuation at different offsets. By assuming the azimuth of the minimum attenuation as the strike direction of fractures, we obtain this direction in the three reservoir units, R1, R2 and R3 at several offsets. The comparison between the estimated directions and those based on core data interpretation is quite satisfactory. This is a good indication about the potential of seismic wave attenuation attribute for fracture characterization.

Our results show that the effect of fractures on seismic wave attenuation is frequency dependent. By modifying the frequency range, the dominant orientation of fractures changes. This is related to scattering and intrinsic attenuation mechanisms that are strongly dependent on frequency. More investigation on this dependence can be useful to provide information about fracture sizes and their fluid content. This a great advantage of attenuation attribute, compared to the classical seismic attributes, such as curvature and ant tracking, which are widely used to extract fracture orientations from seismic data.

We introduce a generalized concept of blending and deblending, establish its models, and accordingly establish a method of deblended-data reconstruction using these models. The generalized models can handle real-life situations by including random encoding into the generalized operators both in the space and time domain, and both at the source and receiver side. We consider an iterative optimization scheme using a closed-loop approach with the generalized-blending and -deblending models, in which the former works for the forward modelling and the latter for the inverse modelling in the closed loop. We established and applied this method to existing real datasets offshore Abu Dhabi. The results show that our method succeeded to fully reconstruct deblended data even from the fully generalized, thus quite complicated blended data.

Foaming is one of the major operating problems in natural gas sweetening alkanolamine plants. The lean methyldiethanolamine (MDEA) samples collected at different times from GASCO (Habshan, Abu Dhabi) sites were analyzed analytically and laboratory foaming studies were carried out to understand the root cause of foaming. Finally, the work aimed to investigate the effect of foam reduction after removal of contaminants such as total organic acid anions and heavy metal ions (chromium and iron) from lean MDEA solutions using bio-polymeric adsorbents. The adsorbents were characterized using SEM and FTIR analysis. In both batch and column studies bio-polymeric adsorbent outperform currently used carbon used by GASCO. The foaming studies after removal of contaminants justified the use of new adsorbents in reclaiming lean MDEA solutions in the plant.

A novel electromagnetic separator (EMS) is designed and developed for removal of heat stable salts (HSS) from industrial lean amine solution used in gas sweetening units. The designed setup is concentric with an outer tubular pipe serving as anode and an inner rod serving as a cathode when connected to an external power supply. The direction of electric field will be radial and perpendicular to the flow path along the channel to enhance the separation of ions at the outlet. The setup has been tested under normal operating conditions. The concentration of HSS was analyzed for each experiment at a fixed voltage and flow rate at different operating time. Various operational parameters, like voltage, flow rate and magnetic field strength are studied to examine the efficiency of the designed system. It was found that the separation efficiency increased on increasing the operational voltage up to 3V, and by decreasing the flow rate and introducing magnetic field on to the system. The developed setup demonstrated potential in removal of HSS from lean amine solutions.

This paper presents a control mechanism based on the actual distance between the Unmanned Aerial Vehicles (UAV) and the tracking structure for UAV visual tracking of pipeline on the ground in a low altitude. The technique includes two parts: structure identification and navigation control. The unburied pipeline is considered as a simple line in 2D image, then the Canny Edge Detector (CED) and Probabilistic Hough Transformation (PHT) are used in image processing to detect edges, identify the pipeline and extract useful parameters (angle and distance in image). For autonomous tracking, the response time, flight stability and tracing accuracy are influenced by the navigation and control performance severely. Thus in this paper the position controller is designed which can calculate the actual distance between the UAV body frame and the detected structure, and the UAV position is regulated by the variant PID controller until the UAV is flying exactly over the pipeline on ground.

The oil and gas industry has a severe problem with chemical corrosion, and microbial contamination of pipelines and infrastructure. The main source of the chemical corrosion is the water that used in digging the crude oil from the ground. It is estimated that the water content in the extracted oil can reach up to 30% in the pipeline. Whilst insufficiently dried oil and gas pipelines have significant general corrosion problems, the industry also has a large need for water pipelines, for example fire/ deluge systems and water injection lines for Enhanced Oil Recovery (EOR). If bacteria are not controlled in these aqueous environments, the consequences for corrosion of the infrastructure is severe and multi parametered. Microbial-initiated corrosion (MIC) is initiated and/or accelerated by the activities of microorganisms, which produce biofilms For example fire water systems are required to be of the “wet riser” style, where the system is full of stagnant water. It is often a challenge to get sufficient biocide around the system to prevent corrosive microbial colonies forming. Most of the corrosion failures of fire systems are due to the microbial corrosion. Similarly water injection lines suffer from corrosion. The usual treatment method is to remove the oxygen to prevent oxygen related corrosion of the steel, but this provides a perfect environment for anaerobes, especially SRBs, which have lead to the souring (production of hydrogen sulfide) of reservoirs. The current approaches to sterilization of lines, such as bleach or oxidizers are incompatible with the aim of reducing corrosion, and many biocides are now prohibited.

Inorganic scale associated with conventional hydrocarbon extraction has been well studied over the past 50 years and the mechanisms of formation, inhibition and removal are now well understood within the industry. For enhanced oil recovery (EOR) significant changes occur within the reservoir as a result of injected chemical or changes in fluid type that are used to increase the oil recovery.

In the case of alkali surfactant polymer (ASP) flooding, the current industry understanding of scale prediction models for such systems is discussed, along with the current inhibitor screening tests to qualify scale inhibitors for squeeze application in a Middle East field. The design of the different squeeze treatments applications for treatment of formation water and injection water production are presented.