As the global HC exploitation paradigm shifts to the unconventional (low-quality) reservoirs; the deep uncertainty in their production processes involved makes the operators, following the Specific Discipline Approach, vulnerable to adopt the trial-and- error methods which can detriment the whole development plan and assimilate irreparable loss upon the foul decisions. Since each engineering discipline may have a piece of puzzle to find the best solution for achieving optimized production rates and economics, we can only hope to achieve the better results if we use a total system (reservoir to sales approach). Pakistan is facing the severe energy crisis, due to which the effective and sensible exploitation of the tight gas reserves has become inevitable. Integrated Asset Modelling (IAM) constructs a thorough way out by increasing communication and literally gets all disciplines "on the same page" by using a common model. The paper is based on designing a full field development plan of a tight gas reservoir (TGRs). It involves developing an integrated reservoir model and evaluating its performance for various reservoir and production scenarios, along with the economic analysis, to come up with an optimum gas field development plan. The methodology is carried out with two approaches (i) Integrated Tank Model (ii) Numerical 3D Model. The paper presents the usefulness of IAM and its systematic approach in production maintenance and optimization, crossfunctional collaboration and in effective field management of tight gas reservoirs. It will present detailed discussion on the economics, process cycle, modelling, optimization, game-changers and exploitation of TGRs along with case studies and intends to give valuable insight to the implementation of this integrated technique to the prevalent energy crisis of the country.
A high-profile and major contributor exploratory well was at the verge of being a work-over candidate due to badly stuck coil tubing (CT) inside wellbore during routine well intervention operations. The situation got even worst when pin hole was established in CT string inside wellbore. The conventional and primary mechanism to release such CT is to operate hydraulic disconnect, which is an integral part of bottomhole motorhead assembly (MHA), by means of applying desired differential hydraulic pressure however, presence of pin hole restricted the desired differential pressure to communicate at motorhead assembly and to operate it. This work highlighted the importance of "back to the basics" phrase when conventional operating procedures failed to be executed and hence termed as "out of the box solution for coiled tubing retrieval". The method proposed in this work can be used by oil and gas professionals as the last resort to retrieve stuck coil tubing with complications like pin hole and failed hydraulic activation mechanism which will certainly avoid major cost exposure and operations complexities associated with rig assisted work-over. In order to activate the hydraulic disconnect inside motorhead assembly of stuck coil tubing, depth of point of communication was estimated, inside volume of coiled tubing upto point of communication was calculated, additional pressure requirement to operate motorhead assembly was identified and heavy mud was pumped at a very slow rate in order to create hydraulic imbalance across coil tubing. Additional pressure due to hydraulic imbalance across coiled tubing was not sufficient to operate motorhead assembly therefore once the heavy mud reached point of communication; by calculation; high pressure pumping was performed in order to give high pressure pulses to motorhead assembly with a hope to activate and release it. All the theoretical calculations and planning based on above went as per plan and coiled tubing was successfully released. The proposed principle of stuck Coil Tubing retrieval is new to oil industry as no literature has been found related to it. It not only saved a high profile well from expensive work-over operation but also the reputation of the exploration and production and service companies involved. The novel approach presented in this paper is inherited from the concepts of fluid mechanics and has been successfully implemented. This methodology has all the merit to be included in the International Well Control Forum (IWCF) as the well control methodology for the stuck coil tubing with pinhole deeper into the well.
Formation damage associated with water blockage is a common problem in oil/gas producing wells. Water blockage is a damage mechanism which occurs when water saturation increases near wellbore, resulting in reduced hydrocarbon saturation and relative permeability to gas. When pore spaces around the well get nearly saturated with water, it reduces gas saturation to near irreducible level that block the gas flow. It decreases the gas production and may recover naturally by extended flow back or excessive drawdown. However, in depleted reservoirs, gas production may completely be lost and shall require chemical treatment. In this paper, a case study has been presented illustrating the complete loss of production of a gas well owing to the water blockage and the treatment mechanism to restore the production (SPE 102383). Well ‘A’ was drilled in Sindh, Pakistan in 2010 in Lower Goru Formation. Later, the well was put on compression and was found on natural decline. By Feb 2019, well was producing 1.14 MMSCFD gas, 6 BPD condensate, and 43 BPD water with 123 psi FWHP. In March 2019, well was shut-in for the pressure build-up (PBU) survey. However, when the well was opened to flow, there was complete loss of production. Identification of the causes of production loss was a major challenge in designing the job. After analysis of well behavior, gradient survey data and formation properties, it was found that the loss of production was attributed to water blockage caused by prolonged exposure of water. Based on above analysis, a stimulation treatment using Volatile Acid System was designed to address the water blockage. The improved cleanup with volatile acid can be expected for two reasons; (1) increased volatility and (2) lower surface & interfacial tensions (SPE-191292-MS). The increased volatility results in lower water saturation and improving relative permeability to gas. Volatile acid system lowers the surface tension and increases the vapor pressure (gas saturation/relative permeability of gas near the damaged zone) and improves the clean-up of spent acid and retained water. In addition, presence of alcohol in acid system helps in achieving deeper penetration into the rock matrix. The proposed solution of Volatile acid system proved successful not only in reviving well's production but also with a gain in production of about 300%.
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