World First Slim Tractor Conveyance in Open Hole Horizontal Wells Under Continuous CO2 Injection for EOR Monitoring - A Case Study from an Onshore Field in the United Arab Emirates

ADNOC has started several years ago few CO2 pilot projects to explore its feasibility for Enhanced Oil Recovery (EOR) in Rumaitha oil field in United Arab Emirates. The CO2 injector wells, to be discussed in this paper, were completed with open-hole horizontal completion, aiming to maximize CO2 injectivity by increasing the contact area between a wellbore and the formation. However, logging these wells for surveillance and intervention has been a challenge, due to the corrosive wellbore environment, tubing minimum restriction and depth reach limitation for both Coiled Tubing (CT) and conventional Tractor conveyance. The current study focusses on using new Slim-hole Tractor, run first time worldwide in CO2 injector wells to convey the logging tools across these long open-hole horizontal wells for rig-less reservoir monitoring and injection optimization. The advanced design Slim Tractor uses high expansion and reciprocating system for increased contact area with the wellbore, to convey logging tools in the horizontal open-hole and cased-hole completions. Several improvements were made over the existing conventional Tractors, such as the increase of pull out of hole capabilities, increased debris tolerance, improved gripping and be able to operate in sour environments. Furthermore, logging while tractoring feature for this advanced Tractor is a key differentiator in horizontal logging to achieve logging objectives the earliest possible while minimizing the acquisition time, reducing the footprint on the well sites, hence less HSE issues and better operations efficiency. This paper presents field experiment conducted on 3 wells in Rumaitha field. The Novel Slim Openhole Tractor was run successfully, first time worldwide in CO2 injector, to convey multiphase production logging tool across a long openhole horizontal completions, in order to determine CO2 zonal injectivity, investigate the presence of possible thief zones, CO2 flow behind the casing. These jobs were conducted real-time to optimize the logging operation and reduce CO2 exposure on the tools. Over 30,000 ft successful tractoring across the 3 horizontal openhole wells. Tractor depth reach exceeded the expectations, almost 100% achieved in 2 wells. The Slim Tractor has also successfully negotiated and passed across multiple washout zones and restrictions encountered, without any issues and the tools were retrieved to surface without any debris clogged on the Tractor arms. Excellent data quality was acquired from the multiphase production logging tool and pulsed Neutron tool during shut-in and flowing at different injection rates in extremely shorter time compared to CT, saving days of operating time. This study helped to delineate the conveyance strategies to be adopted in the upcoming CO2 openhole wells and contributed to enhance the understanding of zonal injectivity distributions across the reservoir. The results will be also incorporated into the reservoir model to understand the effect of injectivity on pore pressure, fracture and faults initiations and their effects on sweep efficiency in EOR and Carbon sequestration in carbon storage projects.

Saturation and Sigma Measurements in Carbonate Formations with Multiple Pulsed Neutron Technologies: Case Study from Southeast Turkey

This paper describes the petrophysical analysis resulting from operation of two independent pulsed neutron logging tools in the same cased hole well. The well was primarily carbonate and included many different subsurface formations located in the Southeast Anatolia Region of Turkey that included the Derdere, Karababa A, B, and C, Karaboğaz, Bozova, and Germav. Computing the mineralogy and saturation in these environments is challenging due to the complexity and low porosity of the formations that included mixed lithologies and organic shale. One of the objectives of this work was to demonstrate how the spectral data from the two tools was not only consistent, but that they could be combined to create an optimal petrophysical interpretation of the lithology, detailed mineralogy, porosity, and saturation of the formations within the well. Both tools employed a pulsed neutron generator capable of emitting 2 x 108 neutrons/second into the ambient formation. One was a 4-detector, 1-11/16-inch diameter reservoir evaluation tool, and the other was a single detector, 3-1/4-inch geochemical spectroscopy tool. In order to obtain the best possible results, a sound logging program was created that involved running the reservoir evaluation tool in 3 different modes of operation. This included the carbon/oxygen (C/O) mode, the sigma mode, and the gas mode. Stationary measurements were also obtained. The geochemical logging tool has only a single mode of operation. The resulting sigma measurements were in complete agreement. The sigma from the geochemical logging tool was corrected for the effects of diffusion. The advantage of the slim-hole reservoir evaluation tool is that the measurements from the 4th detector are diffusion-free. Data from the 1-11/16-inch reservoir evaluation tool from the gas mode did not reveal any bypassed gas zones in the well. Oil saturation was computed with the reservoir evaluation tool based upon three logging passes in the C/O mode. An important component of the interpretation was that it was supported by MCNP modeling that predicted the tool's response for hydrocarbon saturation. Although data from the geochemical spectroscopy tool was not used to determine saturation in this well, the resulting carbon concentration, that included kerogen as well as hydrocarbons, was completely consistent with the saturation computed from the reservoir evaluation tool.

NEURAL NETWORK-BASED APPROACH TO RESISTIVITY LOGS EXPRESS SIMULATION IN REALISTIC MODELS OF COMPLEX TERRIGENOUS SEDIMENTS

The article proposes a new algorithmic approach to resistivity logs simulation based on convolutional neural networks wich allows constructing algorithms for solving forward problems for specific logging tools in detailed models of near-wellbore space with thin layers, accounting for radial resistivity changes, borehole wall irregularities and drilling fluid displacement by the logging tool. Experimental algorithms for expressmodeling for three common Russian galvanic and induсtion logging methods in two-dimensional models of the near-wellbore space have been implemented based on the proposed approach. Logs simulation using the developed neural network algorithms is multi pletimes faster than using numerical solvers. The proposed solutions open up possibilities to use more sophisticated basic geoelectric models of the near-wellbore space. The use of models adequate in complexity to the actual target geological objects will increase the reliability of interpretation results of resistivity logs measured in complex geological conditions.

Locating Source of Water Production and Performing Cost-Effective Rigless Remedial Operations in Deviated Wells Completed with Standalone Sand Screens

Wells that are already drilled and producing are the most viable sources of future earnings for all oilfield operating companies. Keeping these wells producing economically at optimal rates throughout their lifetimes is top priority. With time, some oilfield operating companies face with production related problems, such us water breakthrough. Production logging is well known technique for locating source of water breakthrough in oil and gas producers. In near-vertical, or slightly deviated wells, producing at high rates, traditional production logging tool string can deliver reliable results. On the other side, in deviated wells, producing at small rates, advanced production logging tool is required, due to presence of fluid segregation and recirculation within borehole. Our experience shows that wisely selected logging technique, depending on downhole logging environment, allows to locate source of water production with confidence for planning water shut-off remedial operations. In wells completed with standalone sand screens water shut-off operation might be complicated as often rig is required for pulling out of hole tubing with sand screens. Another method is to perform chemical water shut-off treatment that might be expensive in some cases. Alternative method is to confirm compact sand accumulation in the annulus and set through tubing bridge plug inside sand screens in wells that producing water from bottommost layers. Plug is deployed in wells without pulling out of hole tubing, as it can pass through restrictions, making this rigless intervention fifty times cheaper compared to intervention with rig. Field examples, presented in this paper, describe fit-for-purpose logging approach for locating source of water production accurately and executing unique rigless water shut-off operations in cased wells completed with standalone sand screens to increase hydrocarbons production in cost-effective way. After remedial operations we observed significant decline in water production and increase in oil rates in all wells that were intervened.

A Solution to Tough Logging Conditions (Lwf): Intro to Tough Logging Conditions, Logging While Fishing, Operation Procedure and Conditions

This review work summarised new generation logging techniques such Tough Logging Conditions (TLC) & Logging While Fishing (LWF) and their advancement in drilling operations. The production of Oil & gas from the stage of exploration to production should need a lot of data for economic and safe operations. The conditions of the sub-surface cannot be simply predicted unless with some measured parameters under the LOGGING term. Logging is defined as a continuous record of Petro’s physical parameters of rock against time and depth. Instead of conventional logging techniques of wireline such as SP, Gamma-ray, Neutron, Calliper log, etc, logging while drilling, logging while fishing set them aside of their extended applications. Logging while Fishing is a new generation technology that allows unfailing operations of logging tool by a special installation even in cut and thread operation also aids economic and time enhancement. Tough logging conditions are a technique applied either when the hole has highly deviated or when you need to control the position of a tool. This project includes the study and interpretation of above discussed new generation logs. These tools offer all types of logging carried out on wireline except the SP logging. Logging while drilling provides real-time measurements of physical parameters while drilling operation itself which avoids an additional running of tools causing trips and sticking of drill pipe. The data is stored in the bottom assembled logging tool.

Signals of electromagnetic tool with toroidal coils in highly deviated wells

The research is aimed at expanding the applicability of the logging tool with toroidal coils from vertical to highly deviated wells. Its electromagnetic signals are computed with a three-dimensional finite-difference simulation algorithm on the computing resources of the Siberian Supercomputer Center of SB RAS, which is accompanied by a multi-aspect numerical analysis of the signals. We consider a wide range of geoelectric models with various resistivity contrasts: those of oil-, gas- and water-saturated reservoirs having a different number of horizontal boundaries and varying thicknesses, including the case of fine layering.

Generation of a Complete Profile for Porosity Log While Drilling Complex Lithology by Employing the Artificial Intelligence

The formation porosity of drilled rock is an important parameter that determines the formation storage capacity. The common industrial technique for rock porosity acquisition is through the downhole logging tool. Usually logging while drilling, or wireline porosity logging provides a complete porosity log for the section of interest, however, the operational constraints for the logging tool might preclude the logging job, in addition to the job cost. The objective of this study is to provide an intelligent prediction model to predict the porosity from the drilling parameters. Artificial neural network (ANN) is a tool of artificial intelligence (AI) and it was employed in this study to build the porosity prediction model based on the drilling parameters as the weight on bit (WOB), drill string rotating-speed (RS), drilling torque (T), stand-pipe pressure (SPP), mud pumping rate (Q). The novel contribution of this study is to provide a rock porosity model for complex lithology formations using drilling parameters in real-time. The model was built using 2,700 data points from well (A) with 74:26 training to testing ratio. Many sensitivity analyses were performed to optimize the ANN model. The model was validated using unseen data set (1,000 data points) of Well (B), which is located in the same field and drilled across the same complex lithology. The results showed the high performance for the model either for training and testing or validation processes. The overall accuracy for the model was determined in terms of correlation coefficient (R) and average absolute percentage error (AAPE). Overall, R was higher than 0.91 and AAPE was less than 6.1 % for the model building and validation. Predicting the rock porosity while drilling in real-time will save the logging cost, and besides, will provide a guide for the formation storage capacity and interpretation analysis.

Implementation of Vendor-Independent Stochastic Inversion for Improving Quality and Efficiency of Well Placement on the Field of Novatek Company

The article describes the application of a new stochastic inversion of the deep-azimuthal resistivity data, independent from the tool vendor. The new model was performed on the data from several wells of the PAO «Novatek», that were drilled using deep-azimuthal resistivity tools of two service companies represented in the global oilfield services market. This technology allows to respond in a timely manner when the well approaches the boundaries with contrasting resistivity properties and to avoid exit to unproductive zones. Nowadays, the azimuthal resistivity data is the method with the highest penetration depth for the geosteering in real time. Stochastic inversion is a special mathematical algorithm based on the statistical Monte Carlo method to process the readings of resistivity while drilling in real time and provide a geoelectrical model for making informed decisions when placing horizontal and deviated wells. Until recently, there was no unified approach to calculate stochastic inversion, which allows to perform calculations for various tools. Deep-azimuthal resistivity logging tool vendors have developed their own approaches. This article presents a method for calculating stochastic inversion. This approach was never applied for this kind of azimuthal resistivity data. Additionally, it does not depend on the tool vendor, therefore, allows to compare the data from various tools using a single approach.

Propogation LWD Tool Analysing for Better Saturation Estimation in High Angle Horizontal Well Conditions

Multidepth electromagnetic logging tool is considered as traditional measurements of formation resistivity estimation while drilling. When considering data in wells with high angles trajectory, more than 70 degrees, the resistivity measurements could be affected by several factors associated with geological conditions and logging tool specifications. As the result, during water saturation estimation formation properties could be distorted, which will lead to significant effect of reservoir properties assessment and the design of the horizontal well completion. Within the framework of this paper, various methods of influence on the resistivity readings will be considered, especially with cross boundary effects and reservoir formations with anisotropy. At the same time, propagation resistivity logging technologies while drilling with interpretation and boundary propagation technologies will be observed, which has tilted azimuthal oriented receivers for geosteering service of horizontal wells and additionally helps with take into account of boundary enflurane on standard resistivity logging.

Successful Water Shut Off Strategy for Multilayer Tubingless Wells at Mahakam Field: JM-X Case Study

The objective of this paper is to present the Mechanical Water Shut-Off (MWSO) strategy for multilayer reservoirs on tubingless well. With 10 open perforated reservoirs and no selectivity option, isolation on water producing reservoir will be the main challenge since production is commingled throughout the lifetime of well. Regular production tests performed through a Multiphase Flowmeter equipment on each offshore platform is a first indicator to monitor the evolution of water production in a well. JM-X well has been experiencing water breakthrough since one week after initial perforation and WGR keep increasing following gas production decline. The strategy was initiated by conducting a bottom hole monitoring survey to identify water sources. Production Logging Tool (PLT) was used to precisely monitor pressure, temperature, water holdup, and fluid rate along the wellbore for further water source and production allocation analysis. Once the water source reservoirs have been identified, MWSO operation was requested. There are several types of MWSO equipment that are commonly used in Offshore Mahakam field each of which has selective economic consideration based on the expected well reserve. Considering operation difficulties and cost, MWSO program was made then will be monitored during the operation time to ensure the operation runs safely and smoothly. MWSO strategy on well JM-X was proven to be able to reduce water production from 900 bpd to only 20 bpd with a significant gain of gas production from 3 MMscfd to 9.2 MMscfd and oil production from 200 bpd to 750 bpd.