Planning infill drilling and workover programmes based on reservoir-oriented production logging surveys

Abstract

Wellbore fluid flow profiles in both producers and injectors tend to change over time due to preferential depletion, formation damage, cross-flow, channelling or tubing or casing leaks. These changes can result in excess water production through channelling, coning, non-uniform water breakthrough (fingering) or out-of-zone injection – all leading to uneven flow, pressure and sweep profiles. Ignoring these complications can result in missing key points on reservoir behaviour, selecting wrong units for a 3D full-field flow model or misleading redevelopment planning. Therefore, it would be logical to check for changes in flow geometry before embarking on costly workovers, recompletion or infill drilling programs. This paper compares and integrates the results of conventional Production Logging Tool (PLT) surveys that use spinners and multiphase sensors with those acquired by reservoir-oriented production logging surveys employing a combination of Spectral Noise Logging (SNL) [1,2] and High Precision Temperature (HPT) Logging [3–5]. PLT and HPT-SNL produce similar results when wellbore and completion conditions are good but they may differ dramatically in cases of non-uniform formation damage, channelling behind pipe or plugging of perforations by scale. Generally, HPT-SNL would assess the flow geometry and invaded zones of the reservoir while PLT would point out where fluid enters or leaves the wellbore or tubing. The paper provides case studies from a mature offshore waterflooded field producing a mix of oil, gas, formation water and injection seawater, which complicates the identification of flow geometry and invasion zones and represents a challenge for reservoir engineers in developing proper drilling or workover programmes to target residual reserves [6, 7]. The HPT-SNL-PNL surveys and further studies described here led to successful workovers and drilling. The redevelopment results can be easily assessed by decline curve analysis. Introduction Since 2007, Dubai Petroleum Establishment (DPE) has performed more than 150 integrated PLT-HPT-SNL surveys to monitor vertical wellbore injection and production profiles that resulted in valuable and often surprising findings including unexpected water breakthrough intervals, bypassed oil zones and layers and water channelling behind casing in producers and injectors. These findings, in turn, led to a better understanding of how water propagated through reservoir from injectors to producers and were used to calibrate a 3D full-field flow model and identify optimum infill drilling locations for the redevelopment of the highly fractured crestal area of the field.

Evaluation of different effective parameters during continual gas and water alternating gas (WAG) injections in oil reservoirs

“…Some fraction of the oil in place is bypassed through the movement from reservoir to the wellbore and can not be recovered to the surface. In fi ll drilling in areas where sifnifi cant amount of oil is trapped can be successful method of recovering these amounts of oil from the reservoir (Aslanyan et al, 2014;Awaad et al, 2015;Urban et al, 2016;Parihar et al, 2016). Recovery with CO 2 gas injection was investigated.…”

Infill drilling and well placement assessment for a multi-layered heterogeneous reservoir

“…In such situations, infill drilling with closer spacing is an attractive option to enhance reservoir access that accelerates oil production with more strings and at the same time; it has a chance to improve the oil recovery by increasing water swept volume. In other words, infill drilling targets un-swept oil between the wells that used to be bypassed due to heterogeneity (Aslanyan et al 2014).…”

“…The reservoir fluid flow performance changes for both the injectors and the producers over the time with the maturity of any reservoir due to preferential depletion, formation damage, crossflow, etc., but all of these factors are subjective to the heterogeneity distribution in any specific reservoir (Aslanyan et al 2014). Infill drilling is the most commonly adopted industry practice for several decades because most of the reservoirs around the world are not homogeneous (Driscoll 1974).…”

An Integrated Downhole Production Logging Suite for Locating Water Sources in Oil Production Wells

“…The exact identification of water sources is a crucial step in any further well remedial work to reduce or eliminate them from oil producing wells. [2] …”