In geothermal drilling application, one of the challenges faced by drilling engineers is the optimization of drilling bit which govern the key success of drilling performance. It should be aligned with recent key performance indicator such as meet the subsurface target comprehensively while optimizing the drilling cost. A typical formation in geothermal wells that consists of various types of volcanic and igneous rock should be identified carefully because the high range of hardness and abrasiveness value will respectively affect the bit. Hence, the improvement of conventional drilling bit should be carried out to enhance the drilling performance.
For so many years, Tungsten Carbide Insert (TCI) bits were implemented in the geothermal drilling application because it is believed to be the most effective bit to drill hard formation. However, the TCI bits are limited by the maximum revolution the bit can achieve before the bearing seal fails. In some application, it needs 3 to 4 TCI runs to finish 9.875-in section. Some of the bits were also pulled out of the hole with undergauged condition due to formation abrasiveness. Implementing a conical diamond element (CDE) on a PDC can increase the bit durability. CDE provides significant improvement of wear and impact resistance to the bit. The point loading of this cutter is more concentrated to the formation, allows the bit to remove the rock in more efficient way. It has been discussed that the CDE bit can improve the ROP and meterage drilled, eliminating the tripping time due to bit changes as it does not have KREV limitation, and has a better trajectory control.
Usually, 3-5 TCI bits were used to drilled 9.875-in section in one of geothermal well located in Hululais Field, Sumatera, with average meterage of 200 – 250 m per bit. Drilling dynamics FEA modeling was performed prior to the run of CDE bit to check the drill string vibration and provide stable drilling parameter roadmap for this bit. A CDE bit was run to drill this section and the result was excellent by drilling 600 m in a single run. The ROP was improved by around 35% compared to the maximum TCI's ROP. The bit generated less reactive torque fluctuation compared to TCI, allowed the bit to have better directional control. The CDE bit was pulled out of the hole with good dull grading (2-1-WT-A-X-I-CT-TD). By improving the ROP and eliminating the tripping time, the drilling cost can be reduced.
With the downturn of oil and gas business, geothermal projects in Indonesia is raising. CDE bit is becoming a breakthrough to optimize the drilling operation in by substituting TCI runs with huge amount of potential cost savings.
SAGD is an energy-intensive process with large amount of greenhouse gas (GHG) emissions and required water treatment. One option to reduce emissions and water is to use electromagnetic (EM) heating in either the induction (medium frequency) or radio frequency (RF) ranges. Since the early 1970s, research into the use of RF energy to effectively heat heavy oil reservoirs has led to incremental technology advancements. Since 2009, the Effective Solvent Extraction Incorporating Electromagnetic Heating (ESEIEH™, pronounced "easy") consortium suggested a process named similarly that dielectric heating of oil sand is combined with the injection of a solvent such as propane or butane to reduce bitumen viscosity. In January 2012, the mine face test was declared a success and confirmed the ability to generate, propagate, and distribute electromagnetic heat in an oil sand formation. Phase II of ESEIEH™ exploring scaled pilot tests with horizontal antenna in Suncor’s Dover facility is under developing. To distribute electromagnetic heating into the reservoir creation of desiccated zone and its controlled growth is a key. Since the reservoir is an electrically lossy environment, the growth of desiccated zone as a lossless medium helps the electromagnetic fields to propagate deeper into the formation and associated heating is also further developed within the reservoir. The water will continue to vaporize and move away from the "flashed or desiccated zone" at a rate which diminishes with time. Eventually it reaches the equilibrium condition that it cannot grow with given delivered RF power from the radiating antenna. In this study, the desiccated zone extension at its equilibrium is calculated on the basis of this concept to prevent the zone from collapsing. In this process, water should vaporize and leaks into reservoir to create the flow rate normal to the desiccated zone surface that pushes the water back and grow the zone. Another highlight on this study is to provide the solution for RF-heating avoiding the Lambert’s law or plane-wave assumption. Lambert’s law is (only) accurate and valid in guided-microwave structures or when the EM radiating source is far from the receiving load (relative to the wavelength), such as in optical regime or in telecommunication applications. Although, for heating applications, the maximum energy dissipation of RF waves takes place in the near-field region and not in the far-field region, hence, Lambert’s law does not give a correct solution in these cases. As a result of this study minimum required power is a function of reservoir mobility or in-situ water relative permeability. If efficiency of antenna is not high enough and reservoir mobility is greater than 10-3 then the RF power transmission system could not deliver enough energy to grow the desiccated zone.
Carbonate reservoirs are of strong heterogeneity. Their geological features and dynamic behaviors vary significantly for different types of carbonates. Characterizing the distribution of different types of carbonates and proposing different development strategies are critical for a successful development of carbonate reservoirs. This paper focuses on a super-giant carbonate reservoir with OOIP (Original Oil in Place) of more than 20 billion barrels. However, it has been naturally depleted over the past 40 years. Its reservoir pressure is approaching the bubble point pressure. Therefore, it is critical and urgent to propose optimized water flooding plan for this reservoir.
In this paper, the dataset includes seismic data, well logs, production history, dynamic surveillance data, et al. Firstly, three reservoir types are characterized as good, medium and poor reservoirs based on static and dynamic data. Then, the stacking patterns of different reservoir types are concluded and their distributions are determined, which provide us the foundation to propose customized water flooding plan. Finally, the water flooding performances of different stacking patterns are analyzed and full-field development strategies are proposed based on fine-scale geological modeling and numerical simulation.
Results indicate that stacking pattern has intimate relationship with facies map. For example, the distribution of stacking pattern A, in which good reservoir accounts for the majority, is consistent with the distribution of favorable grainstone shore facies, indicating very good reservoir quality that resulted in higher production rate, longer stable production period, and slow decline. In addition, different offtakes, well patterns, pressure maintenance, well types of different reservoir stacking pattern are determined based on the simulation results and distribution of different stacking patterns. The EUR is increased by more than 20% compared with natural depletion.
This paper offers a reference case of grouping different types of reservoirs and proposing customized water flooding plan, which help engineers and geologists to better develop other similar fields.
Chen, Xin (BGP, Inc., CNPC) | Wei, Xiaodong (BGP, Inc., CNPC) | Wang, Hongmei (BGP, Inc., CNPC) | Zhu, Yunhong (BGP, Inc., CNPC) | Li, Yanjing (BGP, Inc., CNPC) | Xia, Yaliang (BGP, Inc., CNPC) | Xiaohuan, Yan (BGP, Inc., CNPC)
Conventional methods to predict permeability was based on the relationship of porosity-permeability. To improve the accuracy of permeability prediction, seismic constraint and sedimentary facies has often been adopted to improve the porosity accuracy. However, different pore structure possesses different pososity-permeability relationship, the accuracy of permeability prediction cannot be radically improved. To address the problem of permeability prediction in carbonate reservoir, new permeability prediction technique workflow was summarized based on pore structure analysis and multi-parameters seismic inversion. The new workflow includes following steps: 1) divide reservoir types based on the pore structure; 2) establish the rock types identification curve; 3) carry out a rock type inversion and a porosity inversion constrained by seismic impedance; 4) obtain the final permeability prediction volume according to the porosity-permeability relationship and pore structure of core samples. This new workflow breaks the bottleneck that it is difficult for seismic impedance (continuous variable) to constrain rock type (discrete variable). It constrains pore structure (continuous variable) related to rock type instead, and converts it into rock type using multi-parameters seismic inversion. According to the certification of new wells, this workflow have been applied successfully in carbonate reservoir of H oilfield in Middle East. It not only improves the prediction of rock type in space, but also permeability prediction accuracy.
Presentation Date: Monday, September 25, 2017
Start Time: 1:50 PM
Presentation Type: ORAL
Understanding rock attribute variations for a given set of geophysical properties is a key factor for quantitative seismic interpretation and characterization of complex hydrocarbon reservoirs. In this work laboratory ultrasonic measurements are performed on the 10 carbonate samples and waveforms are recorded under different conditions including varying pore-fluid type, confining and pore pressure and partial saturation. P- and S-wave velocities are measured on the basis of the first arrivals and the attenuation of P-waves is estimated by use of the spectrum-ratio method on the transmitted signals. The sensitivity analysis based on the experimental results show that P-wave attenuation is one of the most sensitive indicators for rock porosity and permeability, especially for low porosity rocks. P-wave attenuation is then used to identify the high quality carbonate reservoirs from the actual stratum on the basis of the post-stack seismic data. The prediction results are in good agreement with the well log production reports, validating P-wave attenuation as an effective indicator for directly identifying in-situ carbonate reservoirs.
Presentation Date: Tuesday, September 26, 2017
Start Time: 9:45 AM
Presentation Type: ORAL
We have implemented and compared two numerical schemes for 2.5D finite difference (FD) modeling of directional electromagnetic (EM) wave propagation resistivity logging in a 2D fully anisotropic formation. The FD modeling is primarily developed for well placement and for fully anisotropic formation evaluation to interpret the logging responses of deep directional EM tools. Frequency-domain Maxwell's curl equations and current dipole sources are transformed into spectral domain and then discretized by 2D FD method. The first scheme eliminates the longitudinal components of electric and magnetic fields and sources to obtain a compact 2D FD method, while the second scheme keeps all the six components of electric and magnetic fields to develop a concise scheme. The total region is discretized by a combination of uniform grids inside the tool region and nonuniform girds outside the tool region in the
Presentation Date: Tuesday, September 26, 2017
Start Time: 10:35 AM
Presentation Type: ORAL
Operators are collecting an abundance of produced water data that is often underused. Produced water composition data provide clues as to what geochemical reactions are taking place in the subsurface. This information can be useful for monitoring interwell connectivity, and for predicting and managing oilfield scale resulting from brine supersaturation. Coupling thermodynamic calculations with produced water analysis helps to identify geochemical effects that could impact oil recovery.
This work addresses the difference that reservoir temperature has on geochemical reactions in carbonate reservoirs by comparing data from two offshore fields, and identifying the rock/brine and brine/brine reactions that will impact scale management.
Two seawater flooded chalk fields located close to each other, were selected as candidates for comparison. The temperature of one field is 130°C, while for the other it is 90°C. 6800 produced water samples from these two fields were analysed, and the compositional trends were plotted to identify deviation from conservative (non-reacting) behaviour. The compositional trends were then grouped to identify if there were common features between wells. This analysis was complemented by one dimensional reactive transport modelling to identify which reactions would be consistent with the observed trends.
Two groups of wells were identified within each reservoir based on the produced brine compositional behaviour. Each well group exhibits distinct ion trend behaviour, especially with respect to barium, calcium, strontium and magnesium concentrations – these being divalent cations that are abundant in the formation brines. The breakthrough of sulphate, a component primarily introduced during seawater flooding, varies very significantly between the two groups in each case. In one grouping the sulphate is barely retarded at all, and breaks through at seawater fractions lower than 10%. In the other grouping, however, sulphate does not break through until the seawater fraction in the produced brine exceeds 75%. This retardation of sulphate occurs most strongly in the hotter reservoir, and this may be attributed to the lower solubility of the calcium sulphate mineral anhydrite at higher temperature. The retardation of sulphate then means that barium is produced at higher concentrations, since barite precipitation in the reservoir is thus restricted due to sulphate being the limiting ion. However, some sulphate stripping does occur in the cooler reservoir, despite the higher solubility of anhydrite. Furthermore, in all cases magnesium is retarded, with some groupings exhibiting complete stripping of magnesium from the injected seawater.
The magnesium stripping behaviour is reproduced in the reactive transport models when calcium and magnesium replacement reactions are allowed. This phenomenon has been observed elsewhere in coreflood experiments, and also contributes to the sulphate stripping through promotion of anhydrite precipitation within the rock. This process, which is beneficial in terms of reducing the scale risk, is more pronounced at higher temperatures. Higher temperature chalk reservoirs may thus act as natural sulphate reduction plants, reducing scaling, souring risks and so operating costs of the fields.
Xin, Chen (GRI, BGP, CNPC) | Wei, Xiao-dong (GRI, BGP, CNPC) | Li, Yan-jing (GRI, BGP, CNPC) | Cui, Yi (Petro-China International Iraq, CNODC, CNPC) | Ma, Yingzhe (Petro-China International Iraq, CNODC, CNPC) | Yan, Xiao-huan (GRI, BGP, CNPC) | Xia, Yaliang (GRI, BGP, CNPC) | Wang, Guan (College of Geosciences, China University of Petroleum) | Wang, Xiaotian (College of Geosciences, China University of Petroleum)
Three-dimensional (3D) reservoir models are best created with a combination of well logs and 3D seismic data. However, the effective integration of those results in the reservoir modeling was not easy due to limited seismic resolution. With the increasing quality of seismic data and widely application of new methods, High-resolution seismic stochastic inversion volume was used as a direct input to reduce the uncertainty of the reservoir model in this paper.
Through the past years study, workflows were developed which use the high resolution seismic stochastic inversion as a direct input for reservoir modeling. The workflows mainly include three steps. The first step is target processing. Wavelet transform was applied to achieve noise elimination and resolution improvement. Base on the High-resolution seismic data, the second step is seismic stochastic inversion. After the process of time-depth conversion, the high resolution 3D data from seismic stochastic seismic inversion and well logs data were used to reservoir modeling as a direct input.
Experiment results show that noise elimination and resolution improvement achieved by using wavelet transform brings desirable convenience, high efficiency and good fidelity. The seismic response of sand reservoir in the high resolution seismic section becomes clearer than the seismic data before target processing, and matched with the well log interpretation. As the seismic stochastic inversion process is controlled not only by the acoustic impedance features, variographic model, and histogram, but also by high-resolution seismic data, the possible number of solutions is reduced, thus decreasing the nonuniqueness of the solution. The seismic stochastic inversion results were multiple 3D volumes with the same horizontal resolution of the seismic and with the vertical resolution, which is matched with the well data. The reservoir model base on the high-resolution 3D data from seismic stochastic inversion and well logs data will reduce the uncertainty greatly, especially in the area Where reservoir exhibits strong heterogeneity. A postmortem is presented showing a successful well that were better explained by this model result based on data existing before the well were drilled.
With the increasing quality of seismic data, and the progress of target processing, seismic stochastic inversion and reservoir modeling technology, the high-resolution seismic data will play more and more important role in reservoir modeling. High-resolution seismic stochastic inversion as a direct input for reservoir modeling will reduce the uncertainty of model greatly.
Feng, Yuliang (Pepris Of Sinopec) | Ji, Bingyu (Pepris Of Sinopec) | Sun, Hongjun (Pepris Of Sinopec) | Wan, Xuepeng (Andes Petroleum Ecuador Ltd) | Solis, Ivan (Andes Petroleum Ecuador Ltd) | Tan, Xuequn (Pepris Of Sinopec) | Li, Linlin (Pepris Of Sinopec) | Zhang, Shiyang (Pepris Of Sinopec)
M1 of Mesozoic Cretaceous Napo Formation is a litho-structural composite reservoir, mid-high permeability, with thin sand layers
As liquid production and pressure declined sharply after 8 years' primary drive, in 2003, one injection well was drilled to performance peripheral water injection. The volume and properties of the aquifer were re-estimated according to the production history data and geological analysis. Oil production started to increase and reservoir pressure was restored. The BOPD in 2003 was 950bbl/d, and peaked at 2,300bbl/d in 2007. Later, another two injection wells were drilled to enlarge the sweep volume. But one of them was changed to inject in another zone. Injection volume, pressure, and injection mode were studied and optimized, the oil production peaked at 5,400bbl/d in 2010 as the results of injection optimization. The efforts of real-time waterflooding adjustment extended the high oil production period. By July 2015, RF reached 32.7% with 83.4% water-cut and an ultimate recovery was forecasted to be 45%. Due to effective reservoir management, maximized economic benefit was achieved on the basic economic evaluation. Suggestions on future adjustments were given for waterflooding operations in this field and similar oilfields.
The successful application of waterflooding demonstrated the potential of peripheral water injection in complex reservoirs and the importance of water flooding design. Due to integrated geological study, reservoir performance analysis, and reservoir management, waterflooding operations achieved its best performance with maximum economic benefits.
The propagation of electromagnetic waves within oil production pipes has been studied, taking into account the variation in oil temperature along the pipe. This work shows the development of a simulation model under uncertainties, which is able to simulate the electromagnetic propagation in an inhomogeneous medium by dividing the production pipe into smaller pipe segments, each one approximately homogeneous (constant electrical conductivity). In each segment, the model assumes that the electrical conductivity of oil is a constant and, therefore, the sub pipe is a homogeneous medium. Within each homogeneous medium, the solution is analytically represented by an expansion in basis functions (called modes), that are obtained by the solution of the vector wave equation in a cylinder with lossless walls. Boundary conditions are then applied between adjacent segments to ensure the continuity of both the electric field and the magnetic field, leading into a system of linear equations on the coefficients of the series expansion in basis functions. The solution of this linear system gives the fields in each pipe segment, thus solving the original inhomogeneous problem. In order to account for uncertainties, Monte-Carlo sampling has been used to add small perturbations to predefined oil conductivity profiles along the production pipe. The results show that this model can simulate a thousand of scenarios in less than a second, thus making it ideal for use with optimization algorithms which objective function depends on simulating the propagation of electromagnetic waves inside the well.