Dahlia A . Al-Obaidi | University of Baghdad (original) (raw)

Papers by Dahlia A . Al-Obaidi

Iraqi Geological Journal, 2024

Empirical and statistical methodologies have been established to acquire accurate permeability id... more Empirical and statistical methodologies have been established to acquire accurate permeability identification and reservoir characterization, based on the rock type and reservoir performance. The identification of rock facies is usually done by either using core analysis to visually interpret lithofacies or indirectly based on well-log data. The use of well-log data for traditional facies prediction is characterized by uncertainties and can be time-consuming, particularly when working with large datasets. Thus, Machine Learning can be used to predict patterns more efficiently when applied to large data. Taking into account the electrofacies distribution, this work was conducted to predict permeability for the four wells, FH1, FH2, FH3, and FH19 from the Yamama reservoir in the Faihaa Oil Field, southern Iraq. The framework includes: calculating permeability for uncored wells using the classical method and FZI method. Topological mapping of input space into clusters is achieved using the self-organizing map (SOM), as an unsupervised machinelearning technique. By leveraging data obtained from the four wells, the SOM is effectively employed to forecast the count of electrofacies present within the reservoir. According to the findings, the permeability calculated using the classical method that relies exclusively on porosity is not close enough to the actual values because of the heterogeneity of carbonate reservoirs. Using the FZI method, in contrast, displays more real values and offers the best correlation coefficient. Then, the SOM model and cluster analysis reveal the existence of five distinct groups.

Exploitation of mature oil fields around the world has forced researchers to develop new ways to ... more Exploitation of mature oil fields around the world has forced researchers to develop new ways to optimize reservoir performance from such reservoirs. To achieve that, drilling horizontal wells is an effective method. The effectiveness of this kind of wells is to increase oil withdrawal. The objective of this study is to optimize the location, design, and completion of a new horizontal well as an oil producer to improve oil recovery in a real field located in Iraq. "A" is an oil and gas condensate field located in the Northeast of Iraq. From field production history, it is realized the difficulty to control gas and water production in this kind of complex carbonate reservoir with vertical producer wells. In this study, a horizontal well design with multi-stage completion is studied and proposed to find optimal oil recovery in the southeast region of the selected field. A bulk oil well sector model is used to simulate the fluid flow of a single-porosity/single-permeability model. Then, a sensitivity analysis has been run to optimize; the well trajectory path, different scenarios on well oil and water production potential, and well completion design. The result of the well sector simulation indicates that the well trajectory with an Azimuth of 89 degrees and with a multi-stage completion design has better production performance under water production constraints. Optimum oil production rates of 1000 to 2000 STB/day, as delaying and controlling early gas and water production challenges is achieved.

Multilayer reservoirs are currently modeled as a single zone system by averaging the reservoir pa... more Multilayer reservoirs are currently modeled as a single zone system by averaging the reservoir parameters associated with each reservoir zone. However, this type of modeling is rarely accurate because a single zone system does not account for the fact that each zone's pressure decreases independently. Pressure drop for each zone has an effect on the total output and would result in inter-flow and the premature depletion of one of the zones. Understanding reservoir performance requires a precise estimation of each layer's permeability and skin factor. The Multilayer Transient Analysis is a well-testing technique designed to determine formation properties in more than one layer, and its effectiveness over the past two decades has been demonstrated. In order to conduct MTA, a combination of rate profiles derived from production data and transient rate and pressure measurements at multiple surface rates is necessary. Numerous experimental and analytic approaches to calculating multilayer characteristics, performance, and flow behavior in multilayer systems have emerged. This technology was implemented at the Zubair oil field in southern Iraq. In the last four years, the number of wells producing under saturation pressure has been increased in the Zubair oil field, particularly for the Mishrif and Zubair reservoirs. In the design of secondary and tertiary recovery, the study of the reservoir in the form of an individual layer to determine the pressure, permeability, and damage of each layer with commingled formation is important. This research describes previously available methods, factors that affect Multilayer Transient Analysis an economic indicator of Multilayer Transient Analysis and a case study

Day 2 Tue, May 03, 2022

Energies

Gas and downhole water sink-assisted gravity drainage (GDWS-AGD) is a new process of enhanced oil... more Gas and downhole water sink-assisted gravity drainage (GDWS-AGD) is a new process of enhanced oil recovery (EOR) in oil reservoirs underlain by large bottom aquifers. The process is capital intensive as it requires the construction of dual-completed wells for oil production and water drainage and additional multiple vertical gas-injection wells. The costs could be substantially reduced by eliminating the gas-injection wells and using triple-completed multi-functional wells. These wells are dubbed triple-completion-GDWS-AGD (TC-GDWS-AGD). In this work, we design and optimize the TC-GDWS-AGD oil recovery process in a fictitious oil reservoir (Punq-S3) that emulates a real North Sea oil field. The design aims at maximum oil recovery using a minimum number of triple-completed wells with a gas-injection completion in the vertical section of the well, and two horizontal well sections—the upper section for producing oil (from above the oil/water contact) and the lower section for draining ...

The Gas and Downhole Water Sink-Assisted Gravity Drainage (GDWS-AGD) process functions to enhance... more The Gas and Downhole Water Sink-Assisted Gravity Drainage (GDWS-AGD) process functions to enhance oil recovery by placing vertical gas injectors at the top of the reservoir combined with a series of horizontal wells located in the lower part of the reservoir for oil and water production. The injected gas accumulates to form or enhance a gas cap, while oil and water drain by gravity towards the base of the reservoir due to their heavier densities. To further enhance oil recovery, and to overcome the economic limitations of using vertical gas injectors, multi-completion production wells can also be used for gas injection through their annulus sections. This novel configuration thereby achieves Multi Completion-Gas and Downhole Water Sink-Assisted Gravity Drainage (MC-GDWS-AGD). The feasibility of MC-GDWS-AGD is investigated in this study by numerical simulation of the heterogeneous PUNQ-S3 reservoir, which is surrounded and supported by strong aquifers. The MC-GDWS-AGD process aims to minimize water cut in oil production wells from offshore reservoirs with bottom water drives and strong water coning tendencies. In the combined technologies, the gas is injected through the annulus of 7-inch production casings at the top of the reservoir. Then the same casing is dually completed for two 2-3/8 inch horizontal tubing strings: one above the oil-water contact for oil production, and one beneath that contact to function as the water sink. The two completions are hydraulically isolated within the wellbore by a packer. The lower (water sink) completion employs a submersible pump and water-drainage perforations. The submersible pump drains the accumulation of water from around the well. By doing so it prevents the water from breaking through into the oil column and adversely affecting production through the horizontal oil-producing perforations. The heterogeneous multilayered PUNQ-S3 reservoir, which is surrounded by infinite aquifers, was considered to simulate this process. The MC-GDWS-AGD process simulation is designed to evaluate oil flow rate, cumulative oil production, and water cut in oil production wells. The simulation compares the performance of MC-GDWS-AGD with the GAGD and GDWS-AGD completion configurations. The simulation results reveal similar performance for the MC-GDWS-AGD and GDWS-AGD configurations, for all the parameters considered. The GDWS-AGD method slightly outperforms the MC-GDWS-AGD method by achieving a small increase in cumulative oil production from 1.8x 10 6 m 3 for the GAGD method to 1.83x 10 6 m 3. Both methods exceeded primary recovery in terms of cumulative oil production. Water cut decreased from 74% in the GAGD method to 63% in the MC-GDWS-AGD process. The oil recovery factor achieved by the MC-GDWS-AGD process increased by about 8% compared to that achieved by the GAGD method. The value of the MC-GDWS-AGD process is associated with its effectiveness to improve oil recovery by reducing the water coning, water cut, and improving gas injectivity, and at the same time reducing well costs. This new process allows for gas injection, oil, and water production to be conducted through a single multi-completed wellbore. This configuration also leads to multiple additional economic benefits, some of which are associated with the reduction of operational surface facilities in offshore oil fields.

Certificate of publication for the article titled: "Experimental evaluation of Carbon Dioxide-Ass... more Certificate of publication for the article titled: "Experimental evaluation of Carbon Dioxide-Assisted Gravity Drainage process (CO2-AGD) to improve oil recovery in reservoirs with strong water drive"

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Iraqi Journal of Science, 2020

Macromolecular Characterization of Hydrocarbons for Sustainable Future

The CO2-Assisted Gravity Drainage process (GAGD) has been introduced to become one of the most in... more The CO2-Assisted Gravity Drainage process (GAGD) has been introduced to become one of the most influential process to enhance oil recovery (EOR) methods in both secondary and tertiary recovery through immiscible and miscible mode. Its advantages came from the ability of this process to provide gravity-stable oil displacement for enhancing oil recovery. Vertical injectors for CO2 gas have been placed at the crest of the pay zone to form a gas cap which drain the oil towards the horizontal producing oil wells located above the oil-water-contact. The advantage of horizontal well is to provide big drainage area and small pressure drawdown due to the long penetration. Many simulation and physical models of CO2-AGD process have been implemented at reservoir and ambient conditions to study the effect of this method to improve oil recovery and to examine the most parameters that control the CO2-AGD process. The CO2-AGD process has been developed and tested to increase oil recovery in reservoirs with bottom water drive and strong water coning tendencies. In this study, a scaled prototype 3D simulation model with bottom water drive was used for CO2-assisted gravity drainage. The CO2-AGD process performance was studied. Also the effects of bottom water drive on the performance of immiscible CO2 assisted gravity drainage (enhanced oil recovery and water cut) was investigated. Four different statements scenarios through CO2-AGD process were implemented. Results revealed that: ultimate oil recovery factor increases considerably when implemented CO2-AGD process (from 13.5% to 84.3%). Recovery factor rises with increasing the activity of bottom water drive (from 77.5% to 84.3%). Also, GAGD process provides better reservoir pressure maintenance to keep water cut near 0% limit until gas flood front reaches the production well if the aquifer is active, and stays near 0% limit at all prediction period for limited water drive.

The Gas Assisted Gravity Drainage (GAGD) process has become one of the most important processes t... more The Gas Assisted Gravity Drainage (GAGD) process has become one of the most important processes to enhance oil recovery in both secondary and tertiary recovery stages and through immiscible and miscible modes. Its advantages came from the ability to provide gravity-stable oil displacement for improving oil recovery, when compared with conventional gas injection methods such as Continuous Gas Injection (CGI) and Water-Alternative Gas (WAG). Vertical injectors for CO 2 gas were placed at the top of the reservoir to form a gas cap which drives the oil towards the horizontal oil producing wells which are located above the oil-water-contact. The GAGD process was developed and tested in vertical wells to increase oil recovery in reservoirs with bottom water drive and strong water coning tendencies. Many physical and simulation models of GAGD performance were studied at ambient and reservoir conditions to investigate the effects of this method to enhance the recovery of oil and to examine the most effective parameters that control the GAGD process. A prototype 2D simulation model based on the scaled physical model was built for CO 2-assisted gravity drainage in different statement scenarios. The effects of gas injection rate, gas injection pressure and oil production rate on the performance of immiscible CO 2-assisted gravity drainage-enhanced oil recovery were investigated. The results revealed that the ultimate oil recovery increases considerably with increasing oil production rates. Increasing gas injection rate improves the performance of the process while high pressure gas injection leads to less effective gravity mediated recovery.

Iraqi Journal of Chemical and Petroleum Engineering, 2016

SPE Western Regional Meeting, 2019

Predicting peterophysical parameters and doing accurate geological modeling which are an active r... more Predicting peterophysical parameters and doing accurate geological modeling which are an active research area in petroleum industry cannot be done accurately unless the reservoir formations are classified into subgroups. Also, getting core samples from all wells and characterize them by geologists are very expensive way; therefore, we used the Electro-Facies characterization which is a simple and cost-effective approach to classify one of Iraqi heterogeneous carbonate reservoirs using commonly available well logs. The main goal of this work is to identify the optimum E-Facies units based on principal components analysis (PCA) and model based cluster analysis(MCA) depending on available well logs data for four wells from an Iraqi carbonate oil field. The optimum E-Facies units came from comparing them with geologist classification units for these four wells. Also, we conclude that the value of permeability is not important to get the optimum E-Facies units. Several runs have been tried each with different number of units using the Electro-Facies approach. The results of the techniques show very good match of the tops for various units with the actual ones. This application also shows the power and versatility of electrofacies characterization in improving reservoir descriptions in complex carbonate reservoirs.

Conference: SPE Western Regional MeetingAt: San Jose, California, USA, 2019

A hybrid Gas-Enhanced and Downhole Water Sink-Assisted Gravity Drainage (GDWS-AGD) process has be... more A hybrid Gas-Enhanced and Downhole Water Sink-Assisted Gravity Drainage (GDWS-AGD) process has been suggested to enhance oil recovery by placing vertical injectors for CO2 at the top of the reservoir with a series of horizontal oil-producing and water-drainage wells located above and below the oil-water contact, respectively. The injected gas builds a gas cap that drives the oil to the (upper) oil-producing wells while the bottom water-drainage wells control water cresting. The hybrid process of GDWS-AGD process has been first developed and tested in vertical wells to minimize water cut in reservoirs with bottom water drive and strong water coning tendencies. The wells were dual-completed with 7-inch production casing and 2-3/8 inch tubings and perforated above the oil-water contact (OWC) for oil production and below OWC for water drainage. The two completions were hydraulically isolated inside the well by a packer. The bottom (water sink) completion drained water with a submersible pump. The GDWS-AGD was efficiently adopted to improve oil recovery at the PUNQ saturated oil field. The PUNQ Field has an infinite active aquifer with very strong edge and bottom water drives. A black oil reservoir flow model was implemented for CO2 flooding simulation of the GDWS-AGD process in comparison with the Gas-Assisted Gravity Drainage (GAGD) process. The comparison was performed to obtain the clearest image about the performance of the combined GDWS-AGD process. Next, Design of Experiments (DoE) and proxy modeling were incorporated to find the most sensitive parameters that affect the GDWS-AGD process performance. The candidate parameters are porosity, horizontal and vertical permeability for each layer, radius of aquifer and rock compressibility. In the GDWS-AGD, the produced water not only reduced water cut and coning, but also significantly reduced the reservoir pressure, resulting in improving gas injectivity. In addition, the GDWS-AGD process improved cumulative oil production. More specifically, the results showed that cumulative oil production increased from 3.8*105m3 to 4.7*105m3 and water cut decreased from 97% to 92% in all the horizontal oil producers. For the proxy model, it was cleared from Sobol analysis that the porosity for layer 5 was more influential parameter than others on cumulative oil through GDWS-AGD process with 31% main effects and 0.025% interaction effects, while the horizontal permeability for layer 4 was the most influential parameter with 24% main effects and 1.5% interaction effects. The novelty of GDWS-AGD process comes from its effectiveness to improve oil recovery with reducing the water coning, water cut, and improving gas injectivity. This leads to more economic implementation, especially with respect to the operational surface facilities.

Permeability determination in Carbonate reservoir is a complex problem, due to their capability t... more Permeability determination in Carbonate reservoir is a complex problem, due to their capability to be tight and heterogeneous, also core samples are usually only available for few wells therefore predicting permeability with low cost and reliable accuracy is an important issue, for this reason permeability predictive models become very desirable. This paper will try to develop the permeability predictive model for one of Iraqi carbonate reservoir from core and well log data using the principle of Hydraulic Flow Units (HFUs). HFU is a function of Flow Zone Indicator (FZI) which is a good parameter to determine (HFUs). Histogram analysis, probability analysis and Log-Log plot of Reservoir Quality Index (RQI) versus normalized porosity (ø z) are presented to identify optimal hydraulic flow units. Four HFUs were distinguished in this study area with good correlation coefficient for each HFU (R 2 =0.99), therefore permeability can be predicted from porosity accurately if rock type is known. Conventional core analysis and well log data were obtained in well 1 and 2 in one of carbonate Iraqi oil field. The relationship between core and well log data was determined by Artificial Neural Network (ANN) in cored wells to develop the predictive model and then was used to develop the flow units prediction to un-cored wells. Finally permeability can be calculated in each HFU using effective porosity and mean FZI in these HFUs. Validation of the models evaluated in a separate cored well (Blind-Test) which exists in the same formation. The results showed that permeability prediction from ANN and HFU matched well with the measured permeability from core data with R 2 =0.94 and ARE= 1.04%.

An optimization analysis of drilling process constitutes a powerful tool for operating under desi... more An optimization analysis of drilling process constitutes a powerful tool for operating under desired pressure levels and simultaneously maximizing the penetration rate, which reduces costs and time thus increases the profit. In this study, a composite drilling model (Young-Bourgyen model) of eight functions was used to determine the optimum drilling mechanical parameters (Weight on bit and rotary speed) for an Iraqi oil field. These functions model the effect of most drilling parameters such as formation strength, mud density, formation compaction, weight on bit, rotary speed, tooth dullness, and bit hydraulic on drilling rate. Data are extracted from bit record and drilling report of well BUZ-20 for calculation of eight exponents of the model with regression analysis method. For each formation within the geologic section of drilled well, the drillability constant was calculated .The rate of penetration for the field had been predicted based on constants for every data against depth, and noticeable differences between them were observed. Also, an optimized weight on bit and rotary speed had been calculated for several data point.