Efficient Methodology for Stimulation Candidate Selection and Well Workover Optimization

Abstract

Nigeria is endowed with huge proven gas reserves estimated to be 184 trillion cubic feet (Tcf). It ranks as the seventh holder of natural gas reserves in the world, and the largest in Africa. Nigeria also flares more natural gas than any other country; it accounts for 12.5% of the world's annual gas flared equivalent to $2.0 billion of annual revenue wasted. There is crucial need, therefore, to reduce gas flaring and its environmental impacts, and to derive maximum economic benefits from gas production. Well stimulation consists of several methods used for enhancing the natural producing ability of the reservoir when production rate declines. The purpose of the study is to present a methodology and models for the selection, design and optimization of well stimulation. Production decline curve analysis is combined with economic discounting concepts to develop a model that can be used for optimizing stimulation decisions. The model is presented in the form of a non-linear programming problem subject to the constraints imposed by the production facilities, reservoir productivity and the stimulation budget approved by management. Production data from four stimulation candidate wells, offshore Niger Delta was used to validate the model developed by setting up a maximization problem. Solution to the problem was obtained using non-linear optimization software. The results show that the optimization model can be combined with stimulation treatment modules, developed from industry wide models, to quantify stimulation benefits. Candidate wells were then ranked based on stimulation cost, payout time and stimulation benefit. Proposed methodology and models can be used for stimulation candidate selection, ranking workover programs in a field and in optimizing stimulation decisions.

Effect of Matrix Acidizing on The Performance of Selected Niger Delta Reservoirs

“…The most common acid employed to stimulate production is Hydrochloric (HCL) which is useful in removing calcite materials from reservoirs and widely used in carbonate acidizing [3]. Hydrochloric acid may be combined with Hydrofluoric acid (HF) which dissolves silicate phases from the reservoir rocks [4], and Acetic acid also shows better results in carbonate reservoirs [5] The technical objectives of well stimulation are to remove, reduce, or bypass the formation damage, reduce sand production and clean up the perforation [6]. Formation damage which can be as a result of drilling, completion or production operations in the well can be of three types (a) Absolute permeability damage: The particulate materials block the formation pore spaces thereby reducing permeability [7]; Relative permeability changes which results in an adverse relative permeability effect in highly water saturated zone, thereby creating significant reduction in the apparent relative permeability to oil [8] and viscosity effect due to rock mineral alterations [9].…”

Assessment of oil-producing wells by means of stimulation approach through matrix acidizing: a case study in the Azraq region

“…In some applications, mixtures of HCl and hydrofluoric acids (HF) are implemented, which boost the dissolving of sandstones and other silicate content in the reservoir rocks (Tang et al 2002;Thomas et al 2002;Patton et al 2003;Shafiq and Mahmud 2016;Rabbani et al 2018). The technical objectives of well stimulation are to eliminate or bypass the formation damage, therefore reducing the debris production, and the gravel packs are eventually cleaned up (Ifeanyi et al 2015;Ugbenyen 2011;Wilfred and Umeleuma 2015).…”